docs(tests): added tests tutorial for widget

docs/developer/widget_development/tutorial_tests.md

@@ -0,0 +1,81 @@
+(developer.widget_development.tutorial_tests)=
+
+# 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`](https://docs.pytest.org/en/stable/) along with
+the [`pytest-qt`](https://pytest-qt.readthedocs.io/en/latest/) 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:
+
+1. **`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.
+
+2. **`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.
+
+3. **`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.
+
+4. **`clean_singleton` Fixture**: This fixture cleans up any singleton instances used in error popups, preventing
+   interference between tests.
+
+5. **`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.
+
+```{note}
+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. 
+
+```
+
+````{dropdown} View code: Conftest with Fixtures
+:icon: code-square
+:animate: fade-in-slide-down
+```{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`](user.widgets.positioner_box) widget,
+utilizing the fixtures mentioned above:
+
+````{dropdown} View code: PositionerBox Widget Unit Tests
+:icon: code-square
+:animate: fade-in-slide-down
+```{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.

docs/developer/widget_development/widget_development.md

@@ -54,4 +54,5 @@ hidden: false
 bec_dispatcher
 widget_base_class
 widget_tutorial
+tutorial_tests
 ```