stbt Python API¶

Testcases are Python functions stored in the test-pack git repository under tests/*.py. The function name must begin with test_.

Example¶

import stbt

# You can import your own helper libraries from the test-pack.
import dialogues


def test_that_pressing_EPG_opens_the_guide():
    # We recommend starting each testcase with setup steps so that
    # the testcase can be run no matter what state the device-under-
    # test is in. Note that you can call other Python functions
    # defined elsewhere in your test-pack.
    if dialogues.modal_dialogue_is_up():
        dialogues.close_modal_dialogue()

    # Send an infrared keypress:
    stbt.press("KEY_EPG")

    # Verify that the device-under-test has reacted appropriately:
    stbt.wait_for_match("guide.png")

Controlling the system-under-test¶

Remote control¶

stbt.press: Send the specified key-press to the system-under-test.
stbt.pressing: Press and hold a key until some other condition is met.
stbt.press_and_wait: Press a key, then wait for the screen to change, then wait for it to stop changing.
stbt.press_until_match: Call press as many times as necessary to find the specified image.

Network-based protocols¶

Some devices (such as the Roku and some Smart TVs) can be controlled via HTTP or other network protocols. You can use any Python networking library to make network requests to such devices (to install third-party Python libraries see Customising the test-run environment). We recommend the Python requests library, which is already installed.

Alexa and Google Home¶

stbt.play_audio_file: Play an audio clip (for example “Alexa, play Teletubbies”) to test integration of your device with voice-controlled devices like Alexa or Google Home.

Verifying the system-under-test’s behaviour¶

Searching for an image¶

stbt.wait_for_match: Search for the specified image in the video stream; raise stbt.MatchTimeout if not found within a certain timeout.
stbt.match: Search for the specified image in a single video frame; return a truthy/falsey stbt.MatchResult.
stbt.match_all: Search for all instances of the specified image in a single video frame.

Use stbt.match with assert and stbt.wait_until for a more flexible alternative to stbt.wait_for_match. For example, to wait for an image to disappear:

stbt.press("KEY_CLOSE")
assert wait_until(lambda: not stbt.match("guide.png"))

Searching for text using OCR (optical character recognition)¶

stbt.match_text: Search for the specified text in a single video frame; return a truthy/falsey stbt.TextMatchResult.
stbt.ocr: Read the text present in a video frame.

Searching for motion¶

stbt.wait_for_motion: Search for motion in the video stream; raise stbt.MotionTimeout if no motion is found within a certain timeout.
stbt.detect_motion: Generator that yields a sequence of one stbt.MotionResult for each frame processed from the system-under-test, indicating whether any motion was detected.

Miscellaneous video APIs¶

stbt.is_screen_black: Check whether the video frame is completely black.

Audio APIs¶

Audio input:

stbt.get_rms_volume: Calculate the average RMS volume over a given duration.
stbt.wait_for_volume_change: Wait for changes in the RMS audio volume. Can detect the start of content playback or unmuting; bleeps or clicks while navigating the UI; or beeps in an A/V sync video.
stbt.audio_chunks: Low-level API to get raw audio samples for custom analysis.

Audio output:

stbt.play_audio_file: Play an audio file through the Stb-tester Node’s “audio out” jack. Useful for testing integration of your device with Alexa or Google Home.

Region, mask, and frame¶

Some of the above functions take an optional region parameter that allows you to restrict the search to a specific rectangular region of the video frame. See stbt.Region.

Some of the above functions take an optional mask parameter that allows you to specify a more complex region than the single rectangle you can specify with region. A mask is a black & white image where white pixels specify which parts of the frame to check, and black pixels specify which parts of the frame to ignore.

The functions that operate on a single frame at a time (match, match_text, ocr, etc) take an optional frame parameter. This is in the OpenCV BGR format, as returned by frames, get_frame, and load_image. If frame is not specified, a frame will be grabbed from the system-under-test. This is useful for writing unit-tests (self-tests) for those functions. If you write your own helper functions we recommend that you follow this pattern.

Custom image processing¶

Stb-tester can give you raw video frames for you to do your own image processing with OpenCV’s “cv2” Python API. Stb-tester’s video frames are numpy.ndarray objects, which is the same format that OpenCV uses.

stbt.frames: Generator that yields frames captured from the system-under-test. Example usage: for frame in stbt.frames(): ...
stbt.get_frame: Return the latest video frame.
stbt.load_image: Load an image from disk.
stbt.crop: Crop an image using a stbt.Region.

To save a frame to disk, use cv2.imwrite. Note that any file you write to the current working directory will appear as an artifact in the test-run results.

Logging¶

stbt.draw_text: Write the specified text on this test-run’s video recording.

Anything you write to stdout or stderr appears in the test-run’s logfile in stb-tester’s test-results viewer.

Metrics¶

For some customers we run Prometheus and Grafana on your Stb-tester Portal. (Prometheus is an open-source time-series database for metrics; Grafana is an open-source dashboard & reporting tool driven by the data in Prometheus.) If this is enabled on your Portal, you can log metrics to Prometheus using the following APIs:

stbt.prometheus.Counter
stbt.prometheus.Gauge
stbt.prometheus.Histogram

Utilities¶

stbt.as_precondition: Mark test failures as test errors in some parts of your testcase.
stbt.FrameObject: Base class for user-defined Page Objects, which are a layer of abstraction between your testcases and the stbt image processing APIs.
stbt.get_config: Read a value from the test-pack’s Configuration files.
stbt.wait_until: Wait until a condition becomes true, or until a timeout.

Exceptions¶

If your testcase raises one of the following exceptions, it is considered a test failure:

AssertionError (raised by Python’s assert statement).
stbt.MatchTimeout (raised by stbt.wait_for_match).
stbt.MotionTimeout (raised by stbt.wait_for_motion).
stbt.UITestFailure: Inherit from this if you need to define your own test-failure exceptions.

Any other exception is considered a test error. For details see Test failures vs. errors.

API reference¶

stbt.apply_ocr_corrections¶

stbt.apply_ocr_corrections(text, corrections=None)¶

Applies the same corrections as stbt.ocr’s corrections parameter.

This is available as a separate function so that you can use it to post-process old test artifacts using new corrections.

Parameters

text (str) – The text to correct.
corrections (dict) – See stbt.ocr.

stbt.as_precondition¶

stbt.as_precondition(message)¶

Context manager that replaces test failures with test errors.

Stb-tester’s reports show test failures (that is, UITestFailure or AssertionError exceptions) as red results, and test errors (that is, unhandled exceptions of any other type) as yellow results. Note that wait_for_match, wait_for_motion, and similar functions raise a UITestFailure when they detect a failure. By running such functions inside an as_precondition context, any UITestFailure or AssertionError exceptions they raise will be caught, and a PreconditionError will be raised instead.

When running a single testcase hundreds or thousands of times to reproduce an intermittent defect, it is helpful to mark unrelated failures as test errors (yellow) rather than test failures (red), so that you can focus on diagnosing the failures that are most likely to be the particular defect you are looking for. For more details see Test failures vs. errors.

Parameters: message (str) – A description of the precondition. Word this positively: “Channels tuned”, not “Failed to tune channels”.
Raises: PreconditionError if the wrapped code block raises a UITestFailure or AssertionError.

Example:

def test_that_the_on_screen_id_is_shown_after_booting():
    channel = 100

    with stbt.as_precondition("Tuned to channel %s" % channel):
        mainmenu.close_any_open_menu()
        channels.goto_channel(channel)
        power.cold_reboot()
        assert channels.is_on_channel(channel)

    stbt.wait_for_match("on-screen-id.png")

stbt.audio_chunks¶

stbt.audio_chunks(time_index=None)¶

Low-level API to get raw audio samples.

audio_chunks returns an iterator of AudioChunk objects. Each one contains 100ms to 5s of mono audio samples (see AudioChunk for the data format).

audio_chunks keeps a buffer of 10s of audio samples. time_index allows the caller to access these old samples. If you read from the returned iterator too slowly you may miss some samples. The returned iterator will skip these old samples and silently re-sync you at -10s. You can detect this situation by comparing the .end_time of the previous chunk to the .time of the current one.

Parameters: time_index (int or float) – Time from which audio samples should be yielded. This is an epoch time compatible with time.time(). Defaults to the current time as given by time.time().
Returns: An iterator yielding AudioChunk objects
Return type: Iterator[AudioChunk]

stbt.AudioChunk¶

class stbt.AudioChunk(array, dtype=None, order=None, time=None, rate=48000)¶

A sequence of audio samples.

An AudioChunk object is what you get from audio_chunks. It is a subclass of numpy.ndarray. An AudioChunk is a 1-D array containing audio samples in 32-bit floating point format (numpy.float32) between -1.0 and 1.0.

In addition to the members inherited from numpy.ndarray, AudioChunk defines the following attributes:

Variables

time (float) – The wall-clock time of the first audio sample in this chunk, as number of seconds since the unix epoch (1970-01-01T00:00:00Z). This is the same format used by the Python standard library function time.time.
rate (int) – Number of samples per second. This will typically be 48000.
duration (float) – The duration of this audio chunk in seconds.
end_time (float) – time + duration.

AudioChunk supports slicing using Python’s [x:y] syntax, so the above attributes will be updated appropriately on the returned slice.

stbt.ConfigurationError¶

exception stbt.ConfigurationError¶

Bases: Exception

An error with your stbt configuration file.

stbt.ConfirmMethod¶

class stbt.ConfirmMethod(value)¶

An enumeration.

NONE = 'none'¶

ABSDIFF = 'absdiff'¶

NORMED_ABSDIFF = 'normed-absdiff'¶

stbt.crop¶

stbt.crop(frame, region)¶

Returns an image containing the specified region of frame.

Parameters: frame (stbt.Frame or numpy.ndarray) – An image in OpenCV format (for example as returned by frames, get_frame and load_image, or the frame parameter of MatchResult).
Returns: An OpenCV image (numpy.ndarray) containing the specified region of the source frame. This is a view onto the original data, so if you want to modify the cropped image call its copy() method first.

stbt.detect_motion¶

stbt.detect_motion(timeout_secs=10, noise_threshold=None, mask=None, region=Region.ALL, frames=None)¶

Generator that yields a sequence of one MotionResult for each frame processed from the device-under-test’s video stream.

The MotionResult indicates whether any motion was detected.

Use it in a for loop like this:

for motionresult in stbt.detect_motion():
    ...

In most cases you should use wait_for_motion instead.

Parameters

timeout_secs (int or float or None) – A timeout in seconds. After this timeout the iterator will be exhausted. Thas is, a for loop like for m in detect_motion(timeout_secs=10) will terminate after 10 seconds. If timeout_secs is None then the iterator will yield frames forever. Note that you can stop iterating (for example with break) at any time.
noise_threshold (float) –
The amount of noise to ignore. This is only useful with noisy analogue video sources. Valid values range from 0 (all differences are considered noise; a value of 0 will never report motion) to 1.0 (any difference is considered motion).

This defaults to 0.84. You can override the global default value by setting noise_threshold in the [motion] section of .stbt.conf.
mask (str or numpy.ndarray) –
A black & white image that specifies which part of the image to search for motion. White pixels select the area to analyse; black pixels select the area to ignore.

This can be a string (a filename that will be resolved as per load_image) or a single-channel image in OpenCV format.

If you specify region, the mask must be the same size as the region. Otherwise the mask must be the same size as the frame.
region (Region) – Only analyze the specified region of the video frame.
frames (Iterator[stbt.Frame]) – An iterable of video-frames to analyse. Defaults to stbt.frames().

stbt.detect_pages¶

stbt.detect_pages(frame=None, candidates=None, test_pack_root='')¶

Find Page Objects that match the given frame.

This function tries each of the Page Objects defined in your test-pack (that is, subclasses of stbt.FrameObject) and returns an instance of each Page Object that is visible (according to the object’s is_visible property).

This is a Python generator that yields 1 Page Object at a time. If your code only consumes the first object (like in the example below), detect_pages will try each Page Object class until it finds a match, yield it to your code, and then it won’t waste time trying other Page Object classes:

page = next(stbt.detect_pages())

To get all the matching pages you can iterate like this:

for page in stbt.detect_pages():
    print(type(page))

Or create a list like this:

pages = list(stbt.detect_pages())

Parameters

frame (stbt.Frame) – The video frame to process; if not specified, a new frame is grabbed from the device-under-test by calling stbt.get_frame.
candidates (Sequence[Type[stbt.FrameObject]]) – The Page Object classes to try. Note that this is a list of the classes themselves, not instances of those classes. If candidates isn’t specified, detect_pages will use static analysis to find all of the Page Objects defined in your test-pack.
test_pack_root (str) – A subdirectory of your test-pack to search for Page Object definitions, used when candidates isn’t specified. Defaults to the entire test-pack.

Return type

Iterator[stbt.FrameObject]

Returns

An iterator of Page Object instances that match the given frame.

Added in v32.

stbt.draw_text¶

stbt.draw_text(text, duration_secs=3)¶

Write the specified text to the output video.

Parameters

text (str) – The text to write.
duration_secs (int or float) – The number of seconds to display the text.

stbt.find_selection_from_background¶

stbt.find_selection_from_background(image, max_size, min_size=None, frame=None, mask=Region.ALL, threshold=25, erode=True)¶

Checks whether frame matches image, calculating the region where there are any differences. The region where frame doesn’t match the image is assumed to be the selection. This allows us to simultaneously detect the presence of a screen (used to implement a stbt.FrameObject class’s is_visible property) as well as finding the selection.

For example, to find the selection of an on-screen keyboard, image would be a screenshot of the keyboard without any selection. You may need to construct this screenshot artificially in an image editor by merging two different screenshots.

Unlike stbt.match, image must be the same size as frame.

Parameters

image (str or numpy.ndarray) – The background to match against. It can be the filename of a PNG file on disk, or a numpy array containing the pixel data in 8-bit BGR format. If it has an alpha channel, any transparent pixels are masked out (that is, the alpha channel is ANDed with mask). This image must be the same size as frame.
max_size (tuple of 2 ints (width, height)) – The maximum size of the differing region. If the differences between image and frame are larger than this in either dimension, the function will return a falsey result.
min_size (tuple of 2 ints (width, height)) – The minimum size of the differing region (optional). If the differences between image and frame are smaller than this in either dimension, the function will return a falsey result.
frame (stbt.Frame or numpy.ndarray) – If this is specified it is used as the video frame to search in; otherwise a new frame is grabbed from the device-under-test. This is an image in OpenCV format (for example as returned by stbt.frames and stbt.get_frame).
mask (stbt.Region or numpy.ndarray) – Specifies an area within the image to check. If it’s a numpy array (image) it should be a single-channel black-and-white image where black pixels are masked out (ignored).
threshold (int) – Threshold for differences between image and frame for it to be considered a difference. This is a colour distance between pixels in image and frame. 0 means the colours have to match exactly. 255 would mean that even white (255, 255, 255) would match black (0, 0, 0).
erode (bool) – By default we pass the thresholded differences through an erosion algorithm to remove noise or small anti-aliasing differences. If your selection is a single line less than 3 pixels wide, set this to False.

Returns

An object that will evaluate to true if image and frame matched with a difference smaller than max_size. The object has the following attributes:

matched (bool) – True if the image and the frame matched with a difference smaller than max_size.
region (stbt.Region) – The bounding box that contains the selection (that is, the differences between image and frame).
mask_region (stbt.Region) – The region of the frame that was analysed, as given in the function’s mask parameter.
image (stbt.Image) – The reference image given to find_selection_from_background.
frame (stbt.Frame) – The video-frame that was analysed.

Added in v32.

stbt.Frame¶

class stbt.Frame(array, dtype=None, order=None, time=None, _draw_sink=None)¶

A frame of video.

A Frame is what you get from stbt.get_frame and stbt.frames. It is a subclass of numpy.ndarray, which is the type that OpenCV uses to represent images. Data is stored in 8-bit, 3 channel BGR format.

In addition to the members inherited from numpy.ndarray, Frame defines the following attributes:

Variables: time (float) – The wall-clock time when this video-frame was captured, as number of seconds since the unix epoch (1970-01-01T00:00:00Z). This is the same format used by the Python standard library function time.time.

stbt.FrameObject¶

class stbt.FrameObject(frame=None)¶

Base class for user-defined Page Objects.

FrameObjects are Stb-tester’s implementation of the Page Object pattern. A FrameObject is a class that uses Stb-tester APIs like stbt.match() and stbt.ocr() to extract information from the screen, and it provides a higher-level API in the vocabulary and user-facing concepts of your own application.

Based on Martin Fowler’s PageObject diagram¶

Stb-tester uses a separate instance of your FrameObject class for each frame of video captured from the device-under-test (hence the name “Frame Object”). Stb-tester provides additional tooling for writing, testing, and maintenance of FrameObjects.

To define your own FrameObject class:

Derive from stbt.FrameObject.
Define an is_visible property (using Python’s @property decorator) that returns True or False.
Define any other properties for information that you want to extract from the frame.
Inside each property, when you call an image-processing function (like stbt.match or stbt.ocr) you must specify the parameter frame=self._frame.

The following behaviours are provided automatically by the FrameObject base class:

Truthiness: A FrameObject instance is considered “truthy” if it is visible. Any other properties (apart from is_visible) will return None if the object isn’t visible.
Immutability: FrameObjects are immutable, because they represent information about a specific frame of video – in other words, an instance of a FrameOject represents the state of the device-under-test at a specific point in time. If you define any methods that change the state of the device-under-test, they should return a new FrameObject instance instead of modifying self.
Caching: Each property will be cached the first time is is used. This allows writing testcases in a natural way, while expensive operations like ocr will only be done once per frame.

The FrameObject base class defines several convenient methods and attributes (see below).

For more details see Object Repository in the Stb-tester manual.

Added in v30: _fields and refresh.

_fields¶: A tuple containing the names of the public properties.

__init__(frame=None)¶

The default constructor takes an optional frame of video; if the frame is not provided, it will grab a frame from the device-under-test.

If you override the constructor in your derived class (for example to accept additional parameters), make sure to accept an optional frame parameter and supply it to the super-class’s constructor.

__repr__()¶: The object’s string representation includes all its public properties.

__bool__()¶: Delegates to is_visible. The object will only be considered True if it is visible.

__eq__(other)¶: Two instances of the same FrameObject type are considered equal if the values of all the public properties match, even if the underlying frame is different. All falsey FrameObjects of the same type are equal.

__ne__(other)¶: Return self!=value.

__lt__(other)¶: Return self<value.

__le__(other)¶: Return self<=value.

__gt__(other)¶: Return self>value.

__ge__(other)¶: Return self>=value.

__hash__()¶: Two instances of the same FrameObject type are considered equal if the values of all the public properties match, even if the underlying frame is different. All falsey FrameObjects of the same type are equal.

refresh(frame=None, **kwargs)¶

Returns a new FrameObject instance with a new frame. self is not modified.

refresh is used by navigation functions that modify the state of the device-under-test.

By default refresh returns a new object of the same class as self, but you can override the return type by implementing refresh in your derived class.

Any additional keyword arguments are passed on to __init__.

stbt.frames¶

stbt.frames(timeout_secs=None)¶

Generator that yields video frames captured from the device-under-test.

For example:

for frame in stbt.frames():
    # Do something with each frame here.
    # Remember to add a termination condition to `break` or `return`
    # from the loop, or specify `timeout_secs` — otherwise you'll have
    # an infinite loop!
    ...

stbt.get_config¶

stbt.get_config(section, key, default=NoDefault, type_=str)¶

Read the value of key from section of the test-pack configuration file.

For example, if your configuration file looks like this:

[test_pack]
stbt_version = 30

[my_company_name]
backend_ip = 192.168.1.23

then you can read the value from your test script like this:

backend_ip = stbt.get_config("my_company_name", "backend_ip")

This searches in the .stbt.conf file at the root of your test-pack, and in the config/test-farm/<hostname>.conf file matching the hostname of the stb-tester device where the script is running. Values in the host-specific config file override values in .stbt.conf. See Configuration files for more details.

Test scripts can use get_config to read tags that you specify at run-time: see Automatic configuration keys.

Raises ConfigurationError if the specified section or key is not found, unless default is specified (in which case default is returned).

stbt.get_frame¶

stbt.get_frame()¶

Grabs a video frame from the device-under-test.

Return type: stbt.Frame
Returns: The most recent video frame in OpenCV format.

Most Stb-tester APIs (stbt.match, stbt.FrameObject constructors, etc.) will call get_frame if a frame isn’t specified explicitly.

If you call get_frame twice very quickly (faster than the video-capture framerate) you might get the same frame twice. To block until the next frame is available, use stbt.frames.

To save a frame to disk pass it to cv2.imwrite. Note that any file you write to the current working directory will appear as an artifact in the test-run results.

stbt.get_rms_volume¶

stbt.get_rms_volume(duration_secs=3, stream=None)¶

Calculate the average RMS volume of the audio over the given duration.

For example, to check that your mute button works:

stbt.press('KEY_MUTE')
time.sleep(1)  # <- give it some time to take effect
assert get_rms_volume().amplitude < 0.001  # -60 dB

Parameters

duration_secs (int or float) – The window over which you should average, in seconds. Defaults to 3s in accordance with short-term loudness from the EBU TECH 3341 specification.
stream (Iterator[AudioChunk]) – Audio stream to measure. Defaults to audio_chunks().

Raises

ZeroDivisionError – If duration_secs is shorter than one sample or stream contains no samples.

Returns

An object with the following attributes:

amplitude (float) – The RMS amplitude over the specified window. This is a value between 0.0 (absolute silence) and 1.0 (a full-range square wave).
time (float) – The start of the window, as number of seconds since the unix epoch (1970-01-01T00:00Z). This is compatible with time.time() and stbt.Frame.time.
duration_secs (float) – The window size, in seconds. Typically this will be the same as passed into get_rms_volume().

stbt.Grid¶

class stbt.Grid(region, cols=None, rows=None, data=None)¶

A grid with items arranged left to right, then down.

For example a keyboard, or a grid of posters, arranged like this:

ABCDE
FGHIJ
KLMNO

All items must be the same size, and the spacing between them must be consistent.

This class is useful for converting between pixel coordinates on a screen, to x & y indexes into the grid positions.

Parameters

region (Region) – Where the grid is on the screen.
cols (int) – Width of the grid, in number of columns.
rows (int) – Height of the grid, in number of rows.
data – A 2D array (list of lists) containing data to associate with each cell. The data can be of any type. For example, if you are modelling a grid-shaped keyboard, the data could be the letter at each grid position. If data is specified, then cols and rows are optional.

class Cell(index, position, region, data)¶

A single cell in a Grid.

Don’t construct Cells directly; create a Grid instead.

Variables

index (int) – The cell’s 1D index into the grid, starting from 0 at the top left, counting along the top row left to right, then the next row left to right, etc.
position (Position) –
The cell’s 2D index (x, y) into the grid (zero-based). For example in this grid “I” is index 8 and position (x=3, y=1):
```
ABCDE
FGHIJ
KLMNO
```
region (Region) – Pixel coordinates (relative to the entire frame) of the cell’s bounding box.
data – The data corresponding to the cell, if data was specified when you created the Grid.

get(index=None, position=None, region=None, data=None)¶

Retrieve a single cell in the Grid.

For example, let’s say that you’re looking for the selected item in a grid by matching a reference image of the selection border. Then you can find the (x, y) position in the grid of the selection, like this:

selection = stbt.match("selection.png")
cell = grid.get(region=selection.region)
position = cell.position

You must specify one (and only one) of index, position, region, or data. For the meaning of these parameters see Grid.Cell.

A negative index counts backwards from the end of the grid (so -1 is the bottom right position).

region doesn’t have to match the cell’s pixel coordinates exactly; instead, this returns the cell that contains the center of the given region.

Returns: The Grid.Cell that matches the specified query; raises IndexError if the index/position/region is out of bounds or the data is not found.

stbt.Image¶

class stbt.Image¶

An image, possibly loaded from disk.

This is a subclass of numpy.ndarray, which is the type that OpenCV uses to represent images.

In addition to the members inherited from numpy.ndarray, Image defines the following attributes:

Variables

filename (str or None) – The filename that was given to stbt.load_image.
absolute_filename (str or None) – The absolute path resolved by stbt.load_image.
relative_filename (str or None) – The path resolved by stbt.load_image, relative to the root of the test-pack git repo.

Added in v32.

stbt.is_screen_black¶

stbt.is_screen_black(frame=None, mask=None, threshold=None, region=Region.ALL)¶

Check for the presence of a black screen in a video frame.

Parameters

frame (stbt.Frame or numpy.ndarray) – If this is specified it is used as the video frame to check; otherwise a new frame is grabbed from the device-under-test. This is an image in OpenCV format (for example as returned by frames and get_frame).
mask (str or numpy.ndarray) –
A black & white image that specifies which part of the image to analyse. White pixels select the area to analyse; black pixels select the area to ignore.

This can be a string (a filename that will be resolved as per stbt.load_image) or a single-channel image in OpenCV format.

If you specify region, the mask must be the same size as the region. Otherwise the mask must be the same size as the frame.
threshold (int) – Even when a video frame appears to be black, the intensity of its pixels is not always 0. To differentiate almost-black from non-black pixels, a binary threshold is applied to the frame. The threshold value is in the range 0 (black) to 255 (white). The global default (20) can be changed by setting threshold in the [is_screen_black] section of .stbt.conf.
region (Region) – Only analyze the specified region of the video frame.

Returns

An object that will evaluate to true if the frame was black, or false if not black. The object has the following attributes:

black (bool) – True if the frame was black.
frame (stbt.Frame) – The video frame that was analysed.

stbt.Keyboard¶

class stbt.Keyboard(graph=None, mask=None, navigate_timeout=20)¶

Models the behaviour of an on-screen keyboard.

You customize for the appearance & behaviour of the keyboard you’re testing by specifying two things:

A Directed Graph that specifies the navigation between every key on the keyboard. For example: When A is selected, pressing KEY_RIGHT on the remote control goes to B, and so on.
A Page Object that tells you which key is currently selected on the screen. See the page parameter to enter_text and navigate_to.

The constructor takes the following parameters:

Parameters

graph – Deprecated; will be removed in the next release. Instead, first create the Keyboard object, and then use add_key, add_transition, add_edgelist, and add_grid to build the model of the keyboard.
mask (str) – A mask to use when calling stbt.press_and_wait to determine when the current selection has finished moving. If the search page has a blinking cursor you need to mask out the region where the cursor can appear, as well as any other regions with dynamic content (such as a picture-in-picture with live TV). See stbt.press_and_wait for more details about the mask.
navigate_timeout (int or float) – Timeout (in seconds) for navigate_to. In practice navigate_to should only time out if you have a bug in your model or in the real keyboard under test.

For example, let’s model the lowercase keyboard from the YouTube search page on Apple TV:

# 1. Specify the keyboard's navigation model
# ------------------------------------------

kb = stbt.Keyboard()

# The 6x6 grid of letters & numbers:
kb.add_grid(stbt.Grid(stbt.Region(x=125, y=175, right=425, bottom=475),
                      data=["abcdef",
                            "ghijkl",
                            "mnopqr",
                            "stuvwx",
                            "yz1234",
                            "567890"]))
# The 3x1 grid of special keys:
kb.add_grid(stbt.Grid(stbt.Region(x=125, y=480, right=425, bottom=520),
                      data=[[" ", "DELETE", "CLEAR"]]))

# The `add_grid` calls (above) defined the transitions within each grid.
# Now we need to specify the transitions from the bottom row of numbers
# to the larger keys below them:
#
#     5 6 7 8 9 0
#     ↕ ↕ ↕ ↕ ↕ ↕
#     SPC DEL CLR
#
# Note that `add_transition` adds the symmetrical transition (KEY_UP)
# by default.
kb.add_transition("5", " ", "KEY_DOWN")
kb.add_transition("6", " ", "KEY_DOWN")
kb.add_transition("7", "DELETE", "KEY_DOWN")
kb.add_transition("8", "DELETE", "KEY_DOWN")
kb.add_transition("9", "CLEAR", "KEY_DOWN")
kb.add_transition("0", "CLEAR", "KEY_DOWN")

# 2. A Page Object that describes the appearance of the keyboard
# --------------------------------------------------------------

class SearchKeyboard(stbt.FrameObject):
    """The YouTube search keyboard on Apple TV"""

    @property
    def is_visible(self):
        # Implementation left to the reader. Should return True if the
        # keyboard is visible and focused.
        ...

    @property
    def selection(self):
        """Returns the selected key.

        Used by `Keyboard.enter_text` and `Keyboard.navigate_to`.

        Note: The reference image (selection.png) is carefully cropped
        so that it will match the normal keys as well as the larger
        "SPACE", "DELETE" and "CLEAR" keys. The middle of the image
        (where the key's label appears) is transparent so that it will
        match any key.
        """
        m = stbt.match("selection.png", frame=self._frame)
        if m:
            return kb.find_key(region=m.region)
        else:
            return None

    # Your Page Object can also define methods for your test scripts to
    # use:

    def enter_text(self, text):
        return kb.enter_text(text.lower(), page=self)

    def clear(self):
        page = kb.navigate_to("CLEAR", page=self)
        stbt.press_and_wait("KEY_OK")
        return page.refresh()

For a detailed tutorial, including an example that handles multiple keyboard modes (lowercase, uppercase, and symbols) see our article Testing on-screen keyboards with Stb-tester.

stbt.Keyboard was added in v31.

Changed in v32:

Added support for keyboards with different modes (such as uppercase, lowercase, and symbols).
Changed the internal representation of the Directed Graph. Manipulating the networkx graph directly is no longer supported.
Removed stbt.Keyboard.parse_edgelist and stbt.grid_to_navigation_graph. Instead, first create the Keyboard object, and then use add_key, add_transition, add_edgelist, and add_grid to build the model of the keyboard.
Removed the stbt.Keyboard.Selection type. Instead, your Page Object’s selection property should return a Key value obtained from find_key.

add_key(name, text=None, region=None, mode=None)¶

Add a key to the model (specification) of the keyboard.

Parameters

name (str) – The text or label you can see on the key.
text (str) – The text that will be typed if you press OK on the key. If not specified, defaults to name if name is exactly 1 character long, otherwise it defaults to "" (an empty string). An empty string indicates that the key doesn’t type any text when pressed (for example a “caps lock” key to change modes).
region (stbt.Region) – The location of this key on the screen. If specified, you can look up a key’s name & text by region using find_key(region=...).
mode (str) – The mode that the key belongs to (such as “lowercase”, “uppercase”, “shift”, or “symbols”) if your keyboard supports different modes. Note that the same key, if visible in different modes, needs to be modelled as separate keys (for example (name="space", mode="lowercase") and (name="space", mode="uppercase")) because their navigation connections are totally different: pressing up from the former goes to lowercase “c”, but pressing up from the latter goes to uppercase “C”. mode is optional if your keyboard doesn’t have modes, or if you only need to use the default mode.

Returns

The added key. This is an object that you can use with add_transition.

Raises

ValueError if the key is already present in the model.

find_key(name=None, text=None, region=None, mode=None)¶

Find a key in the model (specification) of the keyboard.

Specify one or more of name, text, region, and mode (as many as are needed to uniquely identify the key).

For example, your Page Object’s selection property would do some image processing to find the selection on screen, and then use find_key to identify the current key based on the region of that selection.

Returns: An object that unambiguously identifies the key in the model. It has “name”, “text”, “region”, and “mode” attributes. You can use this object as the source or target parameter of add_transition.
Raises: ValueError if the key does not exist in the model, or if it can’t be identified unambiguously (that is, if two or more keys match the given parameters).

find_keys(name=None, text=None, region=None, mode=None)¶

Find matching keys in the model of the keyboard.

This is like find_key, but it returns a list containing any keys that match the given parameters. For example, if there is a space key in both the lowercase and uppercase modes of the keyboard, calling find_keys(text=" ") will return a list of 2 objects [Key(text=" ", mode="lowercase"), Key(text=" ", mode="uppercase")].

This method doesn’t raise an exception; the list will be empty if no keys matched.

add_transition(source, target, keypress, mode=None, symmetrical=True)¶

Add a transition to the model (specification) of the keyboard.

For example: To go from “A” to “B”, press “KEY_RIGHT” on the remote control.

Parameters

source – The starting key. This can be a Key object returned from add_key or find_key; or it can be a dict that contains one or more of “name”, “text”, “region”, and “mode” (as many as are needed to uniquely identify the key using find_key). For convenience, a single string is treated as “name” (but this may not be enough to uniquely identify the key if your keyboard has multiple modes).
target – The key you’ll land on after pressing the button on the remote control. This accepts the same types as source.
keypress (str) – The name of the key you need to press on the remote control, for example “KEY_RIGHT”.

mode (str) –

Optional keyboard mode that applies to both source and target. For example, the two following calls are the same:

add_transition("c", " ", "KEY_DOWN", mode="lowercase")

add_transition({"name": "c", "mode": "lowercase"},
               {"name": " ", "mode": "lowercase"},
               "KEY_DOWN")

symmetrical (bool) – By default, if the keypress is “KEY_LEFT”, “KEY_RIGHT”, “KEY_UP”, or “KEY_DOWN”, this will automatically add the opposite transition. For example, if you call add_transition("a", "b", "KEY_RIGHT") this will also add the transition ("b", "a", "KEY_LEFT)". Set this parameter to False to disable this behaviour. This parameter has no effect if keypress is not one of the 4 directional keys.

Raises

ValueError if the source or target keys do not exist in the model, or if they can’t be identified unambiguously.

add_edgelist(edgelist, mode=None, symmetrical=True)¶

Add keys and transitions specified in a string in “edgelist” format.

Parameters

edgelist (str) –
A multi-line string where each line is in the format <source_name> <target_name> <keypress>. For example, the specification for a qwerty keyboard might look like this:
```
'''
Q W KEY_RIGHT
Q A KEY_DOWN
W E KEY_RIGHT
...
'''
```
The name “SPACE” will be converted to the space character (” “). This is because space is used as the field separator; otherwise it wouldn’t be possible to specify the space key using this format.

Lines starting with “###” are ignored (comments).
mode (str) – Optional mode that applies to all the keys specified in edgelist. See add_key for more details about modes. It isn’t possible to specify transitions between different modes using this edgelist format; use add_transition for that.
symmetrical (bool) – See add_transition.

add_grid(grid, mode=None)¶

Add keys, and transitions between them, to the model of the keyboard.

If the keyboard (or part of the keyboard) is arranged in a regular grid, you can use stbt.Grid to easily specify the positions of those keys. This only works if the columns & rows are all of the same size.

If your keyboard has keys outside the grid, you will still need to specify the transitions from the edge of the grid onto the outside keys, using add_transition. See the example above.

Parameters

grid (stbt.Grid) – The grid to model. The data associated with each cell will be used for the key’s “name” attribute (see add_key).
mode (str) – Optional mode that applies to all the keys specified in grid. See add_key for more details about modes.

Returns

A new stbt.Grid where each cell’s data is a key object that can be used with add_transition (for example to define additional transitions from the edges of this grid onto other keys).

enter_text(text, page, verify_every_keypress=False)¶

Enter the specified text using the on-screen keyboard.

Parameters

text (str) – The text to enter. If your keyboard only supports a single case then you need to convert the text to uppercase or lowercase, as appropriate, before passing it to this method.
page (stbt.FrameObject) –
An instance of a stbt.FrameObject sub-class that describes the appearance of the on-screen keyboard. It must implement the following:
- selection (Key) — property that returns a Key object, as returned from find_key.
When you call enter_text, page must represent the current state of the device-under-test.
verify_every_keypress (bool) –
If True, we will read the selected key after every keypress and assert that it matches the model. If False (the default) we will only verify the selected key corresponding to each of the characters in text. For example: to get from A to D you need to press KEY_RIGHT three times. The default behaviour will only verify that the selected key is D after the third keypress. This is faster, and closer to the way a human uses the on-screen keyboard.

Set this to True to help debug your model if enter_text is behaving incorrectly.

Typically your FrameObject will provide its own enter_text method, so your test scripts won’t call this Keyboard class directly. See the example above.

navigate_to(target, page, verify_every_keypress=False)¶

Move the selection to the specified key.

This won’t press KEY_OK on the target; it only moves the selection there.

Parameters

target – This can be a Key object returned from find_key, or it can be a dict that contains one or more of “name”, “text”, “region”, and “mode” (as many as are needed to identify the key using find_keys). If more than one key matches the given parameters, navigate_to will navigate to the closest one. For convenience, a single string is treated as “name”.
page (stbt.FrameObject) – See enter_text.
verify_every_keypress (bool) – See enter_text.

Returns

A new FrameObject instance of the same type as page, reflecting the device-under-test’s new state after the navigation completed.

stbt.last_keypress¶

stbt.last_keypress()¶

Returns information about the last key-press sent to the device under test.

See the return type of stbt.press.

Added in v32.

stbt.load_image¶

stbt.load_image(filename, flags=None)¶

Find & read an image from disk.

If given a relative filename, this will search in the directory of the Python file that called load_image, then in the directory of that file’s caller, etc. This allows you to use load_image in a helper function, and then call that helper function from a different Python file passing in a filename relative to the caller.

Finally this will search in the current working directory. This allows loading an image that you had previously saved to disk during the same test run.

This is the same lookup algorithm used by stbt.match and similar functions.

Parameters

filename (str) – A relative or absolute filename.
flags – Flags to pass to cv2.imread.

Return type

stbt.Image

Returns

An image in OpenCV format — that is, a numpy.ndarray of 8-bit values. With the default flags parameter this will be 3 channels BGR, or 4 channels BGRA if the file has transparent pixels.

Raises

IOError if the specified path doesn’t exist or isn’t a valid image file.

Changed in v30: Include alpha (transparency) channel if the file has transparent pixels.
Changed in v32: Return type is now stbt.Image, which is a numpy.ndarray sub-class with additional attributes filename, relative_filename and absolute_filename.
Changed in v32: Allows passing an image (numpy.ndarray or stbt.Image) instead of a string, in which case this function returns the given image.

stbt.match¶

stbt.match(image, frame=None, match_parameters=None, region=Region.ALL)¶

Search for an image in a single video frame.

Parameters

image (string or numpy.ndarray) –
The image to search for. It can be the filename of a png file on disk, or a numpy array containing the pixel data in 8-bit BGR format. If the image has an alpha channel, any transparent pixels are ignored.

Filenames should be relative paths. See stbt.load_image for the path lookup algorithm.

8-bit BGR numpy arrays are the same format that OpenCV uses for images. This allows generating reference images on the fly (possibly using OpenCV) or searching for images captured from the device-under-test earlier in the test script.
frame (stbt.Frame or numpy.ndarray) – If this is specified it is used as the video frame to search in; otherwise a new frame is grabbed from the device-under-test. This is an image in OpenCV format (for example as returned by frames and get_frame).
match_parameters (MatchParameters) – Customise the image matching algorithm. See MatchParameters for details.
region (Region) – Only search within the specified region of the video frame.

Returns

A MatchResult, which will evaluate to true if a match was found, false otherwise.

Added in v30: Support transparency in the reference image, and new match method MatchMethod.SQDIFF.

stbt.match_all¶

stbt.match_all(image, frame=None, match_parameters=None, region=Region.ALL)¶

Search for all instances of an image in a single video frame.

Arguments are the same as match.

Returns: An iterator of zero or more MatchResult objects (one for each position in the frame where image matches).

Examples:

all_buttons = list(stbt.match_all("button.png"))

for match_result in stbt.match_all("button.png"):
    # do something with match_result here
    ...

stbt.match_text¶

stbt.match_text(text, frame=None, region=Region.ALL, mode=OcrMode.PAGE_SEGMENTATION_WITHOUT_OSD, lang=None, tesseract_config=None, case_sensitive=False, upsample=True, text_color=None, text_color_threshold=None, engine=None, char_whitelist=None)¶

Search for the specified text in a single video frame.

This can be used as an alternative to match, searching for text instead of an image.

Parameters

text (str) – The text to search for.
frame – See ocr.
region – See ocr.
mode – See ocr.
lang – See ocr.
tesseract_config – See ocr.
upsample – See ocr.
text_color – See ocr.
text_color_threshold – See ocr.
engine – See ocr.
char_whitelist – See ocr.
case_sensitive (bool) – Ignore case if False (the default).

Returns

A TextMatchResult, which will evaluate to True if the text was found, false otherwise.

For example, to select a button in a vertical menu by name (in this case “TV Guide”):

m = stbt.match_text("TV Guide")
assert m.match
while not stbt.match('selected-button.png').region.contains(m.region):
    stbt.press('KEY_DOWN')

Added in v30: The engine parameter and support for Tesseract v4.

Added in v31: The char_whitelist parameter.

stbt.MatchMethod¶

class stbt.MatchMethod(value)¶

An enumeration.

SQDIFF = 'sqdiff'¶

SQDIFF_NORMED = 'sqdiff-normed'¶

CCORR_NORMED = 'ccorr-normed'¶

CCOEFF_NORMED = 'ccoeff-normed'¶

stbt.MatchParameters¶

class stbt.MatchParameters(match_method=None, match_threshold=None, confirm_method=None, confirm_threshold=None, erode_passes=None)¶

Parameters to customise the image processing algorithm used by match, wait_for_match, and press_until_match.

You can change the default values for these parameters by setting a key (with the same name as the corresponding python parameter) in the [match] section of .stbt.conf. But we strongly recommend that you don’t change the default values from what is documented here.

You should only need to change these parameters when you’re trying to match a reference image that isn’t actually a perfect match – for example if there’s a translucent background with live TV visible behind it; or if you have a reference image of a button’s background and you want it to match even if the text on the button doesn’t match.

Parameters

match_method (MatchMethod) – The method to be used by the first pass of stb-tester’s image matching algorithm, to find the most likely location of the reference image within the larger source image. For details see OpenCV’s cv2.matchTemplate. Defaults to MatchMethod.SQDIFF.
match_threshold (float) – Overall similarity threshold for the image to be considered a match. This threshold applies to the average similarity across all pixels in the image. Valid values range from 0 (anything is considered to match) to 1 (the match has to be pixel perfect). Defaults to 0.98.
confirm_method (ConfirmMethod) –
The method to be used by the second pass of stb-tester’s image matching algorithm, to confirm that the region identified by the first pass is a good match.

The first pass often gives false positives: It can report a “match” for an image with obvious differences, if the differences are local to a small part of the image. The second pass is more CPU-intensive, but it only checks the position of the image that the first pass identified. The allowed values are:

ConfirmMethod.NONE

Do not confirm the match. This is useful if you know that the reference image is different in some of the pixels. For example to find a button, even if the text inside the button is different.

ConfirmMethod.ABSDIFF

Compare the absolute difference of each pixel from the reference image against its counterpart from the candidate region in the source video frame.

ConfirmMethod.NORMED_ABSDIFF

Normalise the pixel values from both the reference image and the candidate region in the source video frame, then compare the absolute difference as with ABSDIFF.

This method is better at noticing differences in low-contrast images (compared to the ABSDIFF method), but it isn’t suitable for reference images that don’t have any structure (that is, images that are a single solid color without any lines or variation).

This is the default method, with a default confirm_threshold of 0.70.
confirm_threshold (float) –
The minimum allowed similarity between any given pixel in the reference image and the corresponding pixel in the source video frame, as a fraction of the pixel’s total luminance range.

Unlike match_threshold, this threshold applies to each pixel individually: Any pixel that exceeds this threshold will cause the match to fail (but see erode_passes below).

Valid values range from 0 (less strict) to 1.0 (more strict). Useful values tend to be around 0.84 for ABSDIFF, and 0.70 for NORMED_ABSDIFF. Defaults to 0.70.
erode_passes (int) – After the ABSDIFF or NORMED_ABSDIFF absolute difference is taken, stb-tester runs an erosion algorithm that removes single-pixel differences to account for noise and slight rendering differences. Useful values are 1 (the default) and 0 (to disable this step).

stbt.MatchResult¶

class stbt.MatchResult¶

The result from match.

Variables

time (float) – The time at which the video-frame was captured, in seconds since 1970-01-01T00:00Z. This timestamp can be compared with system time (time.time()).
match (bool) – True if a match was found. This is the same as evaluating MatchResult as a bool. That is, if result: will behave the same as if result.match:.
region (Region) – Coordinates where the image was found (or of the nearest match, if no match was found).
first_pass_result (float) – Value between 0 (poor) and 1.0 (excellent match) from the first pass of stb-tester’s image matching algorithm (see MatchParameters for details).
frame (Frame) – The video frame that was searched, as given to match.
image (Image) – The reference image that was searched for, as given to match.

Changed in v32: The type of the image attribute is now stbt.Image. Previously it was a string or a numpy array.

stbt.MatchTimeout¶

exception stbt.MatchTimeout¶

Bases: _stbt.types.UITestFailure

Exception raised by wait_for_match.

Variables

screenshot (Frame) – The last video frame that wait_for_match checked before timing out.
expected (str) – Filename of the image that was being searched for.
timeout_secs (int or float) – Number of seconds that the image was searched for.

stbt.MotionResult¶

class stbt.MotionResult¶

The result from detect_motion and wait_for_motion.

Variables

time (float) – The time at which the video-frame was captured, in seconds since 1970-01-01T00:00Z. This timestamp can be compared with system time (time.time()).
motion (bool) – True if motion was found. This is the same as evaluating MotionResult as a bool. That is, if result: will behave the same as if result.motion:.
region (Region) – Bounding box where the motion was found, or None if no motion was found.
frame (Frame) – The video frame in which motion was (or wasn’t) found.

stbt.MotionTimeout¶

exception stbt.MotionTimeout¶

Bases: _stbt.types.UITestFailure

Exception raised by wait_for_motion.

Variables

screenshot (Frame) – The last video frame that wait_for_motion checked before timing out.
mask (str or None) – Filename of the mask that was used, if any.
timeout_secs (int or float) – Number of seconds that motion was searched for.

stbt.ocr¶

stbt.ocr(frame=None, region=Region.ALL, mode=OcrMode.PAGE_SEGMENTATION_WITHOUT_OSD, lang=None, tesseract_config=None, tesseract_user_words=None, tesseract_user_patterns=None, upsample=True, text_color=None, text_color_threshold=None, engine=None, char_whitelist=None, corrections=None)¶

Return the text present in the video frame as a Unicode string.

Perform OCR (Optical Character Recognition) using the “Tesseract” open-source OCR engine.

Parameters

frame – If this is specified it is used as the video frame to process; otherwise a new frame is grabbed from the device-under-test. This is an image in OpenCV format (for example as returned by frames and get_frame).
region (Region) – Only search within the specified region of the video frame.
mode (OcrMode) – Tesseract’s layout analysis mode.
lang (str) – The three-letter ISO-639-3 language code of the language you are attempting to read; for example “eng” for English or “deu” for German. More than one language can be specified by joining with ‘+’; for example “eng+deu” means that the text to be read may be in a mixture of English and German. This defaults to “eng” (English). You can override the global default value by setting lang in the [ocr] section of .stbt.conf. You may need to install the tesseract language pack; see installation instructions here.
tesseract_config (dict) – Allows passing configuration down to the underlying OCR engine. See the tesseract documentation for details.
tesseract_user_words (unicode string, or list of unicode strings) – List of words to be added to the tesseract dictionary. To replace the tesseract system dictionary altogether, also set tesseract_config={'load_system_dawg': False, 'load_freq_dawg': False}.

tesseract_user_patterns (unicode string, or list of unicode strings) –

List of patterns to add to the tesseract dictionary. The tesseract pattern language corresponds roughly to the following regular expressions:

tesseract  regex
=========  ===========
\c         [a-zA-Z]
\d         [0-9]
\n         [a-zA-Z0-9]
\p         [:punct:]
\a         [a-z]
\A         [A-Z]
\*         *

upsample (bool) – Upsample the image 3x before passing it to tesseract. This helps to preserve information in the text’s anti-aliasing that would otherwise be lost when tesseract binarises the image. This defaults to True; you should only disable it if you are doing your own pre-processing on the image.
text_color (3-element tuple of integers between 0 and 255, BGR order) – Color of the text. Specifying this can improve OCR results when tesseract’s default thresholding algorithm doesn’t detect the text, for example white text on a light-colored background or text on a translucent overlay.
text_color_threshold (int) – The threshold to use with text_color, between 0 and 255. Defaults to 25. You can override the global default value by setting text_color_threshold in the [ocr] section of .stbt.conf.
engine (OcrEngine) – The OCR engine to use. Defaults to OcrEngine.TESSERACT. You can override the global default value by setting engine in the [ocr] section of .stbt.conf.
char_whitelist (unicode string) – String of characters that are allowed. Useful when you know that the text is only going to contain numbers or IP addresses, for example so that tesseract won’t think that a zero is the letter o. Note that Tesseract 4.0’s LSTM engine ignores char_whitelist.
corrections (dict) –
Dictionary of corrections to replace known OCR mis-reads. Each key of the dict is the text to search for; the value is the corrected string to replace the matching key. If the key is a string, it is treated as plain text and it will only match at word boundaries (for example the string "he saw" won’t match "the saw" nor "he saws"). If the key is a regular expression pattern (created with re.compile) it can match anywhere, and the replacement string can contain backreferences such as "\1" which are replaced with the corresponding group in the pattern (same as Python’s re.sub). Example:
```
corrections={'bad': 'good',
             re.compile(r'[oO]'): '0'}
```
Plain strings are replaced first (in the order they are specified), followed by regular expresions (in the order they are specified).

The default value for this parameter can be set with stbt.set_global_ocr_corrections. If global corrections have been set and this corrections parameter is specified, the corrections in this parameter are applied first.

Added in v30: The engine parameter and support for Tesseract v4.
Added in v31: The char_whitelist parameter.
Added in v32: The corrections parameter.

stbt.OcrEngine¶

class stbt.OcrEngine(value)¶

An enumeration.

TESSERACT = 0¶: Tesseract’s “legacy” OCR engine (v3). Recommended.

LSTM = 1¶: Tesseract v4’s “Long Short-Term Memory” neural network. Not recommended for reading menus, buttons, prices, numbers, times, etc, because it hallucinates text that isn’t there when the input isn’t long prose.

TESSERACT_AND_LSTM = 2¶: Combine results from Tesseract legacy & LSTM engines. Not recommended because it favours the result from the LSTM engine too heavily.

DEFAULT = 3¶: Default engine, based on what is installed.

stbt.OcrMode¶

class stbt.OcrMode(value)¶

Options to control layout analysis and assume a certain form of image.

For a (brief) description of each option, see the tesseract(1) man page.

ORIENTATION_AND_SCRIPT_DETECTION_ONLY = 0¶

PAGE_SEGMENTATION_WITH_OSD = 1¶

PAGE_SEGMENTATION_WITHOUT_OSD_OR_OCR = 2¶

PAGE_SEGMENTATION_WITHOUT_OSD = 3¶

SINGLE_COLUMN_OF_TEXT_OF_VARIABLE_SIZES = 4¶

SINGLE_UNIFORM_BLOCK_OF_VERTICALLY_ALIGNED_TEXT = 5¶

SINGLE_UNIFORM_BLOCK_OF_TEXT = 6¶

SINGLE_LINE = 7¶

SINGLE_WORD = 8¶

SINGLE_WORD_IN_A_CIRCLE = 9¶

SINGLE_CHARACTER = 10¶

SPARSE_TEXT = 11¶

SPARSE_TEXT_WITH_OSD = 12¶

RAW_LINE = 13¶

stbt.play_audio_file¶

stbt.play_audio_file(filename)¶

Play an audio file through the Stb-tester Node’s “audio out” jack.

Useful for testing integration of your device with Alexa or Google Home.

Parameters

filename (str) –

The audio file to play (for example a WAV or MP3 file committed to your test-pack).

Filenames should be relative paths. This uses the same path lookup algorithm as stbt.load_image.

stbt.Position¶

class stbt.Position(x, y)¶: A point with x and y coordinates.

stbt.PreconditionError¶

exception stbt.PreconditionError¶: Exception raised by as_precondition.

stbt.press¶

stbt.press(key, interpress_delay_secs=None, hold_secs=None)¶

Send the specified key-press to the device under test.

Parameters

key (str) –
The name of the key/button.

If you are using infrared control, this is a key name from your lircd.conf configuration file.

If you are using HDMI CEC control, see the available key names here. Note that some devices might not understand all of the CEC commands in that list.
interpress_delay_secs (int or float) –
The minimum time to wait after a previous key-press, in order to accommodate the responsiveness of the device-under-test.

This defaults to 0.3. You can override the global default value by setting interpress_delay_secs in the [press] section of .stbt.conf.
hold_secs (int or float) – Hold the key down for the specified duration (in seconds). Currently this is implemented for the infrared, HDMI CEC, and Roku controls. There is a maximum limit of 60 seconds.

Returns

An object with the following attributes:

key (str) – the name of the key that was pressed.
start_time (float) – the time just before the keypress started (in seconds since the unix epoch, like time.time() and stbt.Frame.time).
end_time (float) – the time when transmission of the keypress signal completed.
frame_before (stbt.Frame) – the most recent video-frame just before the keypress started. Typically this is used by functions like stbt.press_and_wait to detect when the device-under-test reacted to the keypress.

Added in v29: The hold_secs parameter.
Added in v30: Returns an object with keypress timings, instead of None.

stbt.press_and_wait¶

stbt.press_and_wait(key, region=stbt.Region.ALL, mask=None, timeout_secs=10, stable_secs=1, min_size=None)¶

Press a key, then wait for the screen to change, then wait for it to stop changing.

This can be used to wait for a menu selection to finish moving before attempting to OCR at the selection’s new position; or to measure the duration of animations; or to measure how long it takes for a screen (such as an EPG) to finish populating.

Parameters

key (str) – The name of the key to press (passed to stbt.press).
region (stbt.Region) – Only look at the specified region of the video frame.
mask (str or numpy.ndarray) –
A black & white image that specifies which part of the video frame to look at. White pixels select the area to analyse; black pixels select the area to ignore.

This can be a string (a filename that will be resolved as per load_image) or a single-channel image in OpenCV format.

If you specify region, the mask must be the same size as the region. Otherwise the mask must be the same size as the frame.
timeout_secs (int or float) – A timeout in seconds. This function will return a falsey value if the transition didn’t complete within this number of seconds from the key-press.
stable_secs – A duration in seconds. The screen must stay unchanged (within the specified region or mask) for this long, for the transition to be considered “complete”.
min_size (Tuple[int, int]) – A tuple of (width, height), in pixels, for differences to be considered as “motion”. Use this to ignore small differences, such as the blinking text cursor in a search box.

Returns

An object that will evaluate to true if the transition completed, false otherwise. It has the following attributes:

key (str) – The name of the key that was pressed.
frame (stbt.Frame) – If successful, the first video frame when the transition completed; if timed out, the last frame seen.
status (stbt.TransitionStatus) – Either START_TIMEOUT, STABLE_TIMEOUT, or COMPLETE. If it’s COMPLETE, the whole object will evaluate as true.
press_time (float) – When the key-press completed.
animation_start_time (float) – When animation started after the key-press (or None if timed out).
end_time (float) – When animation completed (or None if timed out).
duration (float) – Time from press_time to end_time (or None if timed out).
animation_duration (float) – Time from animation_start_time to end_time (or None if timed out).

All times are measured in seconds since 1970-01-01T00:00Z; the timestamps can be compared with system time (the output of time.time()).

Changed in v32: Use the same difference-detection algorithm as wait_for_motion; region and mask can both be specified at the same time.

stbt.pressing¶

stbt.pressing(key, interpress_delay_secs=None)¶

Context manager that will press and hold the specified key for the duration of the with code block.

For example, this will hold KEY_RIGHT until wait_for_match finds a match or times out:

with stbt.pressing("KEY_RIGHT"):
    stbt.wait_for_match("last-page.png")

The same limitations apply as stbt.press’s hold_secs parameter.

stbt.press_until_match¶

stbt.press_until_match(key, image, interval_secs=None, max_presses=None, match_parameters=None, region=Region.ALL)¶

Call press as many times as necessary to find the specified image.

Parameters

key – See press.
image – See match.
interval_secs (int or float) –
The number of seconds to wait for a match before pressing again. Defaults to 3.

You can override the global default value by setting interval_secs in the [press_until_match] section of .stbt.conf.
max_presses (int) –
The number of times to try pressing the key and looking for the image before giving up and raising MatchTimeout. Defaults to 10.

You can override the global default value by setting max_presses in the [press_until_match] section of .stbt.conf.
match_parameters – See match.
region – See match.

Returns

MatchResult when the image is found.

Raises

MatchTimeout if no match is found after timeout_secs seconds.

stbt.prometheus.Counter¶

class stbt.prometheus.Counter(name, description)¶

Log a cumulative metric that increases over time, to the Prometheus database on your Stb-tester Portal.

Prometheus is an open-source monitoring & alerting tool. A Prometheus Counter tracks counts of events or running totals. See Metric Types and instrumentation best practices in the Prometheus documentation.

Example use cases for Counters:

Number of times the “buffering” indicator or “loading” spinner has appeared.
Number of frames seen with visual glitches or blockiness.
Number of VoD assets that failed to play.

Parameters

name (str) – A unique identifier for the metric. See Metric names in the Prometheus documentation.
description (str) – A longer description of the metric.

Added in v32.

inc(value=1, labels=None)¶

Increment the Counter by the given amount.

Parameters

value (int) – The amount to increase.
labels (Mapping[str,str]) –
Optional dict of label_name: label_value entries. See Labels in the Prometheus documentation.

Warning

Every unique combination of key-value label pairs represents a new time series, which can dramatically increase the amount of memory required to store the data on the Stb-tester Node, on the Stb-tester Portal, and on your Prometheus server. Do not use labels to store dimensions with high cardinality (many different label values), such as programme names or other unbounded sets of values.

stbt.prometheus.Gauge¶

class stbt.prometheus.Gauge(name, description)¶

Log a numerical value that can go up and down, to the Prometheus database on your Stb-tester Portal.

Prometheus is an open-source monitoring & alerting tool. A Prometheus Gauge tracks values like temperatures or current memory usage.

Parameters

name (str) – A unique identifier for the metric. See Metric names in the Prometheus documentation.
description (str) – A longer description of the metric.

Added in v32.

set(value, labels=None)¶

Set the Gauge to the given value.

Parameters

value (float) – The measurement to record.
labels (Mapping[str,str]) – See stbt.prometheus.Counter.

stbt.prometheus.Histogram¶

class stbt.prometheus.Histogram(name, description, buckets)¶

Log measurements, in buckets, to the Prometheus database on your Stb-tester Portal.

Prometheus is an open-source monitoring & alerting tool. A Prometheus Histogram counts measurements (such as sizes or durations) into configurable buckets.

Prometheus Histograms are commonly used for performance measurements:

Channel zapping time.
App launch time.
Time for VoD content to start playing.

Prometheus Histograms allow reporting & alerting on particular quantiles. For example you could configure an alert if the 90th percentile of the above measurements exceeds a certain threshold (that is, the slowest 10% of requests are slower than the threshold).

Parameters

name (str) – A unique identifier for the metric. See Metric names in the Prometheus documentation.
description (str) – A longer description of the metric.
buckets (Sequence[float]) – A list of numbers in increasing order, where each number is the upper bound of the corresponding bucket in the Histogram. With Prometheus you must specify the buckets up-front because the raw measurements aren’t stored, only the counts of how many measurements fall into each bucket.

Added in v32.

log(value, labels=None)¶

Store the given value into the Histogram.

Parameters

value (float) – The measurement to record.
labels (Mapping[str,str]) – See stbt.prometheus.Counter.

stbt.Region¶

class stbt.Region(x, y, width=None, height=None, right=None, bottom=None)¶

Region(x, y, width=width, height=height) or Region(x, y, right=right, bottom=bottom)

Rectangular region within the video frame.

For example, given the following regions a, b, and c:

- 01234567890123
░░░░░░░░
░a░░░░░░
░░░░░░░░
░░░░░░░░
░░░░▓▓▓▓░░▓c▓
░░░░▓▓▓▓░░▓▓▓
░░░░▓▓▓▓░░░░░
░░░░▓▓▓▓░░░░░
   ░░░░░░b░░
   ░░░░░░░░░

>>> a = Region(0, 0, width=8, height=8)
>>> b = Region(4, 4, right=13, bottom=10)
>>> c = Region(10, 4, width=3, height=2)
>>> a.right
8
>>> b.bottom
10
>>> b.center
Position(x=8, y=7)
>>> b.contains(c), a.contains(b), c.contains(b), c.contains(None)
(True, False, False, False)
>>> b.contains(c.center), a.contains(b.center)
(True, False)
>>> b.extend(x=6, bottom=-4) == c
True
>>> a.extend(right=5).contains(c)
True
>>> a.width, a.extend(x=3).width, a.extend(right=-3).width
(8, 5, 5)
>>> c.replace(bottom=10)
Region(x=10, y=4, right=13, bottom=10)
>>> Region.intersect(a, b)
Region(x=4, y=4, right=8, bottom=8)
>>> Region.intersect(a, b) == Region.intersect(b, a)
True
>>> Region.intersect(c, b) == c
True
>>> print(Region.intersect(a, c))
None
>>> print(Region.intersect(None, a))
None
>>> Region.intersect(a)
Region(x=0, y=0, right=8, bottom=8)
>>> Region.intersect()
Region.ALL
>>> quadrant = Region(x=float("-inf"), y=float("-inf"), right=0, bottom=0)
>>> quadrant.translate(2, 2)
Region(x=-inf, y=-inf, right=2, bottom=2)
>>> c.translate(x=-9, y=-3)
Region(x=1, y=1, right=4, bottom=3)
>>> Region(2, 3, 2, 1).translate(b)
Region(x=6, y=7, right=8, bottom=8)
>>> Region.intersect(Region.ALL, c) == c
True
>>> Region.ALL
Region.ALL
>>> print(Region.ALL)
Region.ALL
>>> c.above()
Region(x=10, y=-inf, right=13, bottom=4)
>>> c.below()
Region(x=10, y=6, right=13, bottom=inf)
>>> a.right_of()
Region(x=8, y=0, right=inf, bottom=8)
>>> a.right_of(width=2)
Region(x=8, y=0, right=10, bottom=8)
>>> c.left_of()
Region(x=-inf, y=4, right=10, bottom=6)

x¶: The x coordinate of the left edge of the region, measured in pixels from the left of the video frame (inclusive).

y¶: The y coordinate of the top edge of the region, measured in pixels from the top of the video frame (inclusive).

right¶: The x coordinate of the right edge of the region, measured in pixels from the left of the video frame (exclusive).

bottom¶: The y coordinate of the bottom edge of the region, measured in pixels from the top of the video frame (exclusive).

width¶: The width of the region, measured in pixels.

height¶: The height of the region, measured in pixels.

x, y, right, bottom, width and height can be infinite — that is, float("inf") or -float("inf").

center¶: A stbt.Position specifying the x & y coordinates of the region’s center.

static from_extents()¶

Create a Region using right and bottom extents rather than width and height.

Typically you’d use the right and bottom parameters of the Region constructor instead, but this factory function is useful if you need to create a Region from a tuple.

>>> extents = (4, 4, 13, 10)
>>> Region.from_extents(*extents)
Region(x=4, y=4, right=13, bottom=10)

static bounding_box(*args)¶

Returns: The smallest region that contains all the given regions.

>>> a = Region(50, 20, right=60, bottom=40)
>>> b = Region(20, 30, right=30, bottom=50)
>>> c = Region(55, 25, right=70, bottom=35)
>>> Region.bounding_box(a, b)
Region(x=20, y=20, right=60, bottom=50)
>>> Region.bounding_box(b, b)
Region(x=20, y=30, right=30, bottom=50)
>>> Region.bounding_box(None, b)
Region(x=20, y=30, right=30, bottom=50)
>>> Region.bounding_box(b, None)
Region(x=20, y=30, right=30, bottom=50)
>>> Region.bounding_box(b, Region.ALL)
Region.ALL
>>> print(Region.bounding_box(None, None))
None
>>> print(Region.bounding_box())
None
>>> Region.bounding_box(b)
Region(x=20, y=30, right=30, bottom=50)
>>> Region.bounding_box(a, b, c) == \
...     Region.bounding_box(a, Region.bounding_box(b, c))
True

Changed in v30: bounding_box can take an arbitrary number of region arguments, rather than exactly two.

static intersect(*args)¶

Returns: The intersection of the passed regions, or None if the regions don’t intersect.

Any parameter can be None (an empty Region) so intersect is commutative and associative.

Changed in v30: intersect can take an arbitrary number of region arguments, rather than exactly two.

to_slice()¶: A 2-dimensional slice suitable for indexing a stbt.Frame.

contains(other)¶

Returns: True if other (a Region or Position) is entirely contained within self.

translate(x=None, y=None)¶

Returns: A new region with the position of the region adjusted by the given amounts. The width and height are unaffected.

translate accepts separate x and y arguments, or a single Region.

For example, move the region 1px right and 2px down:

>>> b = Region(4, 4, 9, 6)
>>> b.translate(1, 2)
Region(x=5, y=6, right=14, bottom=12)

Move the region 1px to the left:

>>> b.translate(x=-1)
Region(x=3, y=4, right=12, bottom=10)

Move the region 3px up:

>>> b.translate(y=-3)
Region(x=4, y=1, right=13, bottom=7)

Move the region by another region. This can be helpful if TITLE defines a region relative another UI element on screen. You can then combine the two like so:

>>> TITLE = Region(20, 5, 160, 40)
>>> CELL = Region(140, 45, 200, 200)
>>> TITLE.translate(CELL)
Region(x=160, y=50, right=320, bottom=90)

extend(x=0, y=0, right=0, bottom=0)¶

Returns: A new region with the edges of the region adjusted by the given amounts.

replace(x=None, y=None, width=None, height=None, right=None, bottom=None)¶

Returns: A new region with the edges of the region set to the given coordinates.

This is similar to extend, but it takes absolute coordinates within the image instead of adjusting by a relative number of pixels.

dilate(n)¶

Expand the region by n px in all directions.

>>> Region(20, 30, right=30, bottom=50).dilate(3)
Region(x=17, y=27, right=33, bottom=53)

erode(n)¶

Shrink the region by n px in all directions.

>>> Region(20, 30, right=30, bottom=50).erode(3)
Region(x=23, y=33, right=27, bottom=47)
>>> print(Region(20, 30, 10, 20).erode(5))
None

above(height=inf)¶

Returns: A new region above the current region, extending to the top of the frame (or to the specified height).

below(height=inf)¶

Returns: A new region below the current region, extending to the bottom of the frame (or to the specified height).

right_of(width=inf)¶

Returns: A new region to the right of the current region, extending to the right edge of the frame (or to the specified width).

left_of(width=inf)¶

Returns: A new region to the left of the current region, extending to the left edge of the frame (or to the specified width).

stbt.set_global_ocr_corrections¶

stbt.set_global_ocr_corrections(corrections)¶

Specify default OCR corrections that apply to all calls to stbt.ocr and stbt.apply_ocr_corrections.

See the corrections parameter of stbt.ocr for more details.

We recommend calling this function from tests/__init__.py to ensure it is called before any test script is executed.

stbt.stop_job¶

stbt.stop_job(reason: Optional[str] = None) → None¶

Stop this job after the current testcase exits.

If you are running a job with multiple testcases, or a soak-test, the job will stop when the current testcase exits. Any remaining testcases (that you specified when you started the job) will not be run.

Parameters: reason (str) – Optional message that will be logged.

Added in Stb-tester v31.

stbt.TextMatchResult¶

class stbt.TextMatchResult¶

The result from match_text.

Variables

time (float) – The time at which the video-frame was captured, in seconds since 1970-01-01T00:00Z. This timestamp can be compared with system time (time.time()).
match (bool) – True if a match was found. This is the same as evaluating MatchResult as a bool. That is, if result: will behave the same as if result.match:.
region (Region) – Bounding box where the text was found, or None if the text wasn’t found.
frame (Frame) – The video frame that was searched, as given to match_text.
text (str) – The text that was searched for, as given to match_text.

stbt.TransitionStatus¶

class stbt.TransitionStatus(value)¶

An enumeration.

START_TIMEOUT = 0¶: The transition didn’t start (nothing moved).

STABLE_TIMEOUT = 1¶: The transition didn’t end (movement didn’t stop).

COMPLETE = 2¶: The transition started and then stopped.

stbt.UITestFailure¶

exception stbt.UITestFailure¶

Bases: Exception

The test failed because the device under test didn’t behave as expected.

Inherit from this if you need to define your own test-failure exceptions.

stbt.VolumeChangeDirection¶

class stbt.VolumeChangeDirection(value)¶

An enumeration.

LOUDER = 1¶

QUIETER = -1¶

stbt.VolumeChangeTimeout¶

exception stbt.VolumeChangeTimeout¶: Bases: AssertionError

stbt.wait_for_match¶

stbt.wait_for_match(image, timeout_secs=10, consecutive_matches=1, match_parameters=None, region=Region.ALL, frames=None)¶

Search for an image in the device-under-test’s video stream.

Parameters

image – The image to search for. See match.
timeout_secs (int or float or None) – A timeout in seconds. This function will raise MatchTimeout if no match is found within this time.
consecutive_matches (int) – Forces this function to wait for several consecutive frames with a match found at the same x,y position. Increase consecutive_matches to avoid false positives due to noise, or to wait for a moving selection to stop moving.
match_parameters – See match.
region – See match.
frames (Iterator[stbt.Frame]) – An iterable of video-frames to analyse. Defaults to stbt.frames().

Returns

MatchResult when the image is found.

Raises

MatchTimeout if no match is found after timeout_secs seconds.

stbt.wait_for_motion¶

stbt.wait_for_motion(timeout_secs=10, consecutive_frames=None, noise_threshold=None, mask=None, region=Region.ALL, frames=None)¶

Search for motion in the device-under-test’s video stream.

“Motion” is difference in pixel values between two frames.

Parameters

timeout_secs (int or float or None) – A timeout in seconds. This function will raise MotionTimeout if no motion is detected within this time.
consecutive_frames (int or str) –
Considers the video stream to have motion if there were differences between the specified number of consecutive frames. This can be:
- a positive integer value, or
- a string in the form “x/y”, where “x” is the number of frames with motion detected out of a sliding window of “y” frames.
This defaults to “10/20”. You can override the global default value by setting consecutive_frames in the [motion] section of .stbt.conf.
noise_threshold (float) – See detect_motion.
mask – See detect_motion.
region – See detect_motion.
frames – See detect_motion.

Returns

MotionResult when motion is detected. The MotionResult’s time and frame attributes correspond to the first frame in which motion was detected.

Raises

MotionTimeout if no motion is detected after timeout_secs seconds.

stbt.wait_for_transition_to_end¶

stbt.wait_for_transition_to_end(initial_frame=None, region=stbt.Region.ALL, mask=None, timeout_secs=10, stable_secs=1, min_size=None)¶

Wait for the screen to stop changing.

In most cases you should use press_and_wait to measure a complete transition, but if you need to measure several points during a single transition you can use wait_for_transition_to_end as the last measurement. For example:

keypress = stbt.press("KEY_OK")  # Launch my app
m = stbt.wait_for_match("my-app-home-screen.png")
time_to_first_frame = m.time - keypress.start_time
end = wait_for_transition_to_end(m.frame)
time_to_fully_populated = end.end_time - keypress.start_time

Parameters

initial_frame (stbt.Frame) – The frame of video when the transition started. If None, we’ll pull a new frame from the device under test.
region – See press_and_wait.
mask – See press_and_wait.
timeout_secs – See press_and_wait.
stable_secs – See press_and_wait.

Returns

See press_and_wait.

stbt.wait_for_volume_change¶

stbt.wait_for_volume_change(direction=VolumeChangeDirection.LOUDER, stream=None, window_size_secs=0.4, threshold_db=10.0, noise_floor_amplitude=0.0003, timeout_secs=10)¶

Wait for changes in the RMS audio volume.

This can be used to listen for the start of content, or for bleeps and bloops when navigating the UI. It returns after the first significant volume change. This function tries hard to give accurate timestamps for when the volume changed. It works best for sudden changes like a beep.

This function detects changes in volume using a rolling window. The RMS volume is calculated over a rolling window of size window_size_secs. For every sample this function compares the RMS volume in the window preceeding the sample, to the RMS volume in the window following the sample. The ratio of the two volumes determines whether the volume change is significant or not.

Example: Measure the latency of the mute button:

keypress = stbt.press('KEY_MUTE')
quiet = wait_for_volume_change(
    direction=VolumeChangeDirection.QUIETER,
    stream=audio_chunks(time_index=keypress.start_time))
print "MUTE latency: %0.3f s" % (quiet.time - keypress.start_time)

Example: Measure A/V sync between “beep.png” being displayed and a beep being heard:

video = wait_for_match("beep.png")
audio = wait_for_volume_change(
    stream=audio_chunks(time_index=video.time - 0.5),
    window_size_secs=0.01)
print "a/v sync: %i ms" % (video.time - audio.time) * 1000

Parameters

direction (VolumeChangeDirection) – Whether we should wait for the volume to increase or decrease. Defaults to VolumeChangeDirection.LOUDER.
stream (Iterator returned by audio_chunks) – Audio stream to listen to. Defaults to audio_chunks(). Postcondition: the stream will be positioned at the time of the volume change.
window_size_secs (int) – The time over which the RMS volume should be averaged. Defaults to 0.4 (400ms) in accordance with momentary loudness from the EBU TECH 3341 specification. Decrease this if you want to detect bleeps shorter than 400ms duration.
threshold_db (float) – This controls sensitivity to volume changes. A volume change is considered significant if the ratio between the volume before and the volume afterwards is greater than threshold_db. With threshold_db=10 (the default) and direction=VolumeChangeDirection.LOUDER the RMS volume must increase by 10 dB (a factor of 3.16 in amplitude). With direction=VolumeChangeDirection.QUIETER the RMS volume must fall by 10 dB.
noise_floor_amplitude (float) – This is used to avoid ZeroDivisionError exceptions. The change from an amplitude of 0 to 0.1 is ∞ dB. This isn’t very practical to deal with so we consider 0 amplitude to be this non-zero noise_floor_amplitude instead. It defaults to ~0.0003 (-70dBov). Increase this value if there is some sort of background noise that you want to ignore.
timeout_secs (float) – Timeout in seconds. If no significant volume change is found within this time, VolumeChangeTimeout will be raised and your test will fail.

Raises

VolumeChangeTimeout – If no volume change is detected before timeout_secs.

Returns

An object with the following attributes:

direction (VolumeChangeDirection) – This will be either VolumeChangeDirection.LOUDER or VolumeChangeDirection.QUIETER as given to wait_for_volume_change.
rms_before (see get_rms_volume) – The RMS volume averaged over the window immediately before the volume change. Use result.rms_before.amplitude to get the RMS amplitude as a float.
rms_after (see get_rms_volume) – The RMS volume averaged over the window immediately after the volume change.
difference_db (float) – Ratio between rms_after and rms_before, in decibels.
difference_amplitude (float) – Absolute difference between the rms_after and rms_before. This is a number in the range -1.0 to +1.0.
time (float) – The time of the volume change, as number of seconds since the unix epoch (1970-01-01T00:00:00Z). This is the same format used by the Python standard library function time.time() and stbt.Frame.time.
window_size_secs (float) – The size of the window over which the volume was averaged, in seconds.

stbt.wait_until¶

stbt.wait_until(callable_, timeout_secs=10, interval_secs=0, predicate=None, stable_secs=0)¶

Wait until a condition becomes true, or until a timeout.

Calls callable_ repeatedly (with a delay of interval_secs seconds between successive calls) until it succeeds (that is, it returns a truthy value) or until timeout_secs seconds have passed.

Parameters

callable – any Python callable (such as a function or a lambda expression) with no arguments.
timeout_secs (int or float, in seconds) – After this timeout elapses, wait_until will return the last value that callable_ returned, even if it’s falsey.
interval_secs (int or float, in seconds) – Delay between successive invocations of callable_.
predicate – A function that takes a single value. It will be given the return value from callable_. The return value of this function will then be used to determine truthiness. If the predicate test succeeds, wait_until will still return the original value from callable_, not the predicate value.
stable_secs (int or float, in seconds) – Wait for callable_’s return value to remain the same (as determined by ==) for this duration before returning. If predicate is also given, the values returned from predicate will be compared.

Returns

The return value from callable_ (which will be truthy if it succeeded, or falsey if wait_until timed out). If the value was truthy when the timeout was reached but it failed the predicate or stable_secs conditions (if any) then wait_until returns None.

After you send a remote-control signal to the device-under-test it usually takes a few frames to react, so a test script like this would probably fail:

stbt.press("KEY_EPG")
assert stbt.match("guide.png")

Instead, use this:

import stbt
from stbt import wait_until

stbt.press("KEY_EPG")
assert wait_until(lambda: stbt.match("guide.png"))

wait_until allows composing more complex conditions, such as:

# Wait until something disappears:
assert wait_until(lambda: not stbt.match("xyz.png"))

# Assert that something doesn't appear within 10 seconds:
assert not wait_until(lambda: stbt.match("xyz.png"))

# Assert that two images are present at the same time:
assert wait_until(lambda: stbt.match("a.png") and stbt.match("b.png"))

# Wait but don't raise an exception if the image isn't present:
if not wait_until(lambda: stbt.match("xyz.png")):
    do_something_else()

# Wait for a menu selection to change. Here ``Menu`` is a `FrameObject`
# subclass with a property called `selection` that returns the name of
# the currently-selected menu item. The return value (``menu``) is an
# instance of ``Menu``.
menu = wait_until(Menu, predicate=lambda x: x.selection == "Home")

# Wait for a match to stabilise position, returning the first stable
# match. Used in performance measurements, for example to wait for a
# selection highlight to finish moving:
keypress = stbt.press("KEY_DOWN")
match_result = wait_until(lambda: stbt.match("selection.png"),
                          predicate=lambda x: x and x.region,
                          stable_secs=2)
assert match_result
match_time = match_result.time  # this is the first stable frame
print("Transition took %s seconds" % (match_time - keypress.end_time))

Release notes¶

Changes to the stbt core Python API are version-controlled. You can specify the version you want to use in your .stbt.conf file. See test_pack.stbt_version in the Configuration Reference.

We generally expect that upgrading to new versions will be safe; we strive to maintain backwards compatibility. But there may be some edge cases that affect some users, so this mechanism allows you to upgrade in a controlled manner, and to test the upgrade on a branch first.

v32¶

1 October 2020.

Warning

When upgrading the stb-tester package to v32 locally with pip (for your IDE) please follow these steps to uninstall the previous version first:

pip uninstall stb-tester stbt-premium-stubs stbt-extra-stubs
pip install stb-tester

Major new features:

stbt.Keyboard: Support keyboards with multiple modes (for example lowercase, uppercase, and symbols).
stbt.find_selection_from_background: New function to detect if a page is visible, and simultaneously find the position of the current “selection” or “highlight” on the page.
stbt.ocr:
- Calls to Tesseract are cached if all the parameters are identical (including all the pixels in the frame & region). This cache is persisted on disk between test-jobs. This can greatly speed up calls to ocr when reading common text, for example when navigating menus.
- New corrections parameter: A dict of {bad: good} mappings to correct known OCR mistakes.
- New function stbt.apply_ocr_corrections to apply the same corrections to any string — useful for post-processing old test artifacts using new corrections.
- New function stbt.set_global_ocr_corrections to specify the default value for ocr’s corrections parameter. Call this early in your tests, for example in the top-level of tests/__init__.py.
stbt.press_and_wait: New parameter min_size to ignore motion in small regions (useful when you can’t predict the exact position of those regions by specifying a mask).
stbt.Region:
- New center property that returns a stbt.Position value with x and y attributes.
- stbt.Region.contains accepts a stbt.Position as the argument (previously it only accepted a stbt.Region).
- stbt.Region.translate can take another stbt.Region as its argument, instead of separate x and y coordinates.
stbt.detect_pages: New function to find the Page Objects that are relevant for the current video frame.
stbt.last_keypress: New function that returns information about the last key-press sent to the device under test.
stbt.stop_job: New function to stop a job of multiple testcases or a soak-test.
Pylint plugin new checker: Check that the return value from FrameObject.refresh is used (FrameObjects are immutable, so refresh() returns a new object instead of modifying the object it’s called on).

Changes in behaviour since v31:

stbt.crop: Implicitly clamp at the edges of the frame, if the region extends beyond the frame. Previously, this would have raised an exception. It still raises ValueError if the region is entirely outside of the frame.
stbt.draw_text: Also write text to stderr.
stbt.get_config: Allow None as a default value.
stbt.is_screen_black: Increase default threshold from 10 to 20.
stbt.Keyboard:
- Changed the internal representation of the Directed Graph. Manipulating the networkx graph directly is no longer supported.
- Removed Keyboard.parse_edgelist and grid_to_navigation_graph. Instead, first create the Keyboard object, and then use its add_key, add_transition, add_edgelist, and add_grid methods to build the model of the keyboard.
- Removed the Keyboard.Selection type. Instead, your Page Object’s selection property should return a Key value obtained from Keyboard.find_key.
- The edgelist format now allows key names with “#” in them. Previously anything starting with “#” was treated as a comment. Now comments are lines starting with “###” (three hashes), optionally preceded by whitespace.
- Keyboard.enter_text adds a short inter-press delay when entering the same letter twice, because some keyboard implementations ignore the second keypress if pressed too quickly.
stbt.load_image:
- Fix UnicodeDecodeError when filename is utf8-encoded bytes.
- Allow passing a numpy array.
- Return type changed from numpy.ndarray to stbt.Image, which is a sub-class of numpy.ndarray with the additional attributes filename, relative_filename, and absolute_filename.
stbt.match: Disable the “pyramid” performance optimisation if the reference image has too few non-transparent pixels. This fixes false negatives when the reference image is mostly transparent (for example a thin border of opaque pixels around a large transparent centre).
stbt.MatchResult (the return value from stbt.match): The image attribute is now an instance of stbt.Image. Previously it was a string or a numpy array, depending on what you had passed to stbt.match.
stbt.ocr and stbt.match_text: If region is entirely outside the frame, raise ValueError instead of returning an empty string. (This is likely to be an error in your test-script’s logic, not desired behaviour.) This is now consistent with all the other image-processing APIs such as stbt.match.
stbt.press_and_wait:
- Now uses the same difference-detection algorithm as stbt.wait_for_motion. This algorithm is more tolerant of small noise-like differences (less than 3 pixels wide). To use the previous algorithm, run the following code early in your test script (for example at the top level of tests/__init__.py):
```
stbt.press_and_wait.differ = stbt.StrictDiff
```
- If you were passing a numpy array for the mask parameter, now it needs to be a single-channel image (greyscale) not a 3-channel image (BGR). (But if you were passing the mask as the filename of an image on disk, you don’t need to change anything.)

v31¶

19 September 2019.

Major new features:

Supports test-scripts written in Python 3. Python 2 is still supported, too. When upgrading your test-pack to v31 you will need to specify a Python version in your test-pack’s .stbt.conf file like this:
```
[test_pack]
stbt_version = 31
python_version = 3
```
Valid values are 2 or 3. The test-run environment is Ubuntu 18.04, so you get Python 2.7 or 3.6.

We recommend Python 3 for all new test-packs. For large existing test-packs we will continue to support Python 2 until all our large customers have migrated.
stbt.Keyboard: New API for testing & navigating on-screen keyboards.
stbt.Grid: New API for describing grid-like layouts.

Minor additions, bugfixes & improvements:

stbt.match: Fix false negative when using MatchMethod.SQDIFF and a reference image that is mostly transparent except around the edges (for example to find a “highlight” or “selection” around some dynamic content).
stbt.match: Improve error message when you give it an explicit region that is smaller than the reference image.
stbt.ocr: New parameter char_whitelist. Useful when you’re reading text of a specific format, like the time from a clock, a serial number, or a passcode.
stbt.press_and_wait: Ignore small moiré-like differences between frames (temporal dithering?) seen with Apple TV.
stbt.press_and_wait: Draw motion bounding-box on output video (similar to stbt.wait_for_motion).
stbt.press_and_wait: Add key attribute (the name of the key that was pressed) to the return value.
stbt.Region: The static methods intersect and bounding_box will fail if called on an instance. That is, instead of calling self.intersect(other) you must call stbt.Region.intersect(self, other). Previously, if called on an instance it would silently return a wrong value.
stbt.wait_for_motion: More sensitive to slow motion (such as a slow fade to black) by comparing against the last frame since significant differences were seen, instead of always comparing against the previous frame.
stbt lint improvements:
- New checker stbt-frame-object-get-frame: FrameObject properties must use self._frame, not stbt.get_frame().
- New checker stbt-frame-object-property-press: FrameObject properties must not have side-effects that change the state of the device-under-test by calling stbt.press() or stbt.press_and_wait().
- New checker stbt-assert-true: “assert True” has no effect.
- Teach pylint that assert False is the same as raise AssertionError. This fixes incorrect behaviour of pylint’s “unreachable code” and “inconsistent return statements” checkers.

v30¶

25 February 2019.

Major new features:

The test-job environment has been upgraded from Ubuntu 14.04 to Ubuntu 18.04. This means that any third-party packages that you use in your test-scripts will have been upgraded too.
In particular, Tesseract (the engine used by stbt.ocr) has been upgraded to version 4.0. Overall the OCR accuracy should improve slightly, but there may be regressions or differences in behaviour in some cases.
stbt.match supports transparency in the reference images: Transparent pixels in the reference image will be ignored when looking for a match within the video-frame. To use this feature your reference image must be a PNG with an alpha (transparency) channel. We only support fully-opaque or fully-transparent pixels: any pixels that aren’t fully opaque are treated as fully transparent.
- stbt.load_image will include the image’s alpha (transparency) channel if it had any transparent pixels.
stbt.match: Added new MatchMethod.SQDIFF, and made it the default match method. This works better and more consistently than MatchMethod.SQDIFF_NORMED (the previous default). SQIFF_NORMED doesn’t work at all for completely black images or images with transparency, and it exaggerates differences for dark images. The “certainty” number for the new SQDIFF method is still normalised so that it is a number between 0.0 and 1.0, but the normalisation no longer depends on how bright the images were, so the result is more consistent. The new default match_threshold is 0.98.
- To make upgrading easier, we have configured .stbt.conf in existing customer’s test-packs to use the previous defaults.
stbt.match: Inverted the meaning of confirm_threshold. Now numbers closer to 0 mean “less strict” and numbers closer to 1 mean “more strict”. This is for consistency with match_threshold. The default value has changed accordingly, from 0.3 to 0.7.

If you were overriding the default value, you need to set the new value to (1 - previous_value), for example change 0.16 to 0.84.

Minor additions, bugfixes & improvements:

stbt.FrameObject: Add refresh method, used by navigation functions that modify the state of the device-under-test.
stbt.match allows matching a greyscale reference image against a greyscale frame (for example if you’ve applied some custom pre-processing, such as edge detection, to both the frame & reference images).
stbt.MatchParameters: The match_method and confirm_method can be specified as enums (stbt.MatchMethod and stbt.ConfirmMethod respectively). For example:
```
stbt.MatchParameters(match_method=stbt.MatchMethod.SQDIFF,
                     confirm_method=stbt.ConfirmMethod.NONE)
```
Passing the old string values is still supported for backwards compatibility.
stbt.press now returns an object containing information about the keypress, including the start time & end time of the keypress signal. This is intended to help making performance measurements.
stbt.press respects interpress_delay_secs if hold_secs is specified.
stbt.Region: New methods dilate and erode to grow or shrink the region in all directions.
stbt.Region.bounding_box and stbt.Region.intersect can take more than 2 regions.
Roku HTTP control: Enforce 3 second timeout on all HTTP requests.
stbt-lint improvements:
- Uses pylint 1.8.3 (upgraded from 1.6.4).
- New checker stbt-uncommitted-image: Detects when the filename given to stbt.match (and similar functions) exists on disk, but isn’t committed to git.
- stbt-frame-object-missing-frame: Also checks for missing frame parameter when calling class constructors (not just class methods).
- stbt-unused-return-value: Also checks that the return value of stbt.press_and_wait is used.
- stbt-missing-image: Reports the full path to the missing image (relative to your test-pack root).
- stbt-missing-image: Ignores filenames inside str.replace and re.sub.

v29¶

Minimum version supported by the Stb-tester Platform.