Testing BEC Widgets

Importance of Writing Tests for Widgets

Writing tests for widgets, even for simple ones, is crucial in maintaining the reliability and stability of a software project. Tests help ensure that new contributions don't unintentionally break existing functionality, and they provide a safety net for developers making changes in the future. In the context of the BEC Widgets, testing is particularly important due to the complexity of interactions with external systems like the BEC server.

Testing with Pytest and QtBot

For testing Qt-based applications, we use pytest along with the pytest-qt plugin, which provides the qtbot fixture. qtbot is specifically designed to simplify interactions with Qt applications during testing. It handles the creation, management, and cleanup of widgets, ensuring that your tests are robust and do not leave behind any lingering resources or open windows.

Fixtures for Testing BEC Widgets

Let's break down the key fixtures used in testing BEC Widgets:

qapplication Fixture: This fixture ensures that all Qt applications and widgets are properly closed after each test. It uses qtbot to wait until all top-level widgets are closed, raising an error if any remain open.
rpc_register Fixture: This fixture manages the RPCRegister singleton, ensuring that it is reset after each test. This prevents state from leaking between tests, which could cause unexpected behavior.
bec_dispatcher Fixture: This fixture initializes the BECDispatcher and ensures that all connections are properly disconnected and the BEC client is shut down after each test. Like rpc_register, it resets the singleton after each test.
clean_singleton Fixture: This fixture cleans up any singleton instances used in error popups, preventing interference between tests.
create_widget Helper Function: This function is a helper that should be used in all tests requiring widget creation. It ensures that widgets are properly added to qtbot, which manages their lifecycle during tests. We highly recommend using this function to create widgets in your tests to ensure proper cleanup and compatibility with other autouse fixtures.

These fixtures are automatically applied to all tests within the `tests/unit_tests` directory, ensuring consistency and proper cleanup between tests. You can find all unit test fixtures in the `conftest.py` file located in the `tests/unit_tests` directory of the BEC Widgets repository.

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```{literalinclude} ../../../tests/unit_tests/conftest.py
:language: python
```

Example Test for `PositionerBox`

Below is an example of how to write a simple test for the PositionerBox widget, utilizing the fixtures mentioned above:

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```{literalinclude} ../../../tests/unit_tests/test_positioner_box.py
:language: python
```

Key Points in the Test:

Fixture Use: The positioner_box fixture handles widget creation and mocking of external dependencies. This ensures the test runs in isolation and doesn't rely on actual hardware or network connections.
Assertion Checks: The test includes several assertions to verify that the widget initializes correctly, including checking the setpoint, precision, and step size.

Conclusion

By writing tests like the one shown above, you help ensure that your widget behaves as expected. Tests also provide a way to automatically verify that new changes do not introduce regressions. This is particularly important in a collaborative environment where multiple developers are contributing to the same codebase. Your tests not only safeguard your code but also provide confidence to others that their contributions won't break existing functionality.

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