docs(testing): Add documentation for all public testing methods

CHANGELOG.md

@@ -57,6 +57,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### New features
 
+* Expose shiny.pytest, shiny.run and shiny.playwright modules that allow users to testing their Shiny apps. (#1448, #1456)
+
 * Added busy indicators to provide users with a visual cue when the server is busy calculating outputs or otherwise serving requests to the client. More specifically, a spinner is shown on each calculating/recalculating output, and a pulsing banner is shown at the top of the page when the app is otherwise busy. Use the new `ui.busy_indicator.options()` function to customize the appearance of the busy indicators and `ui.busy_indicator.use()` to disable/enable them. (#918)
 
 * Added support for creating modules using Shiny Express syntax, and using modules in Shiny Express apps. (#1220)

shiny/playwright/__init__.py

@@ -5,12 +5,24 @@
         "The shiny.playwright module requires the playwright package to be installed."
         " Please install it with this command:"
         "\n\n    pip install playwright"
-        "\n\n",
-        "If you are using pytest to test your code,"
-        " you can install the pytest-playwright shim package with this command:",
-        "\n\n    pip install pytest-playwright",
     )
+# If `pytest` is installed...
+try:
+    import pytest  # noqa: F401 # pyright: ignore[reportUnusedImport, reportMissingTypeStubs]
+
+    # At this point, `playwright` and `pytest` are installed.
+    # Try to make sure `pytest-playwright` is installed
+    try:
+        import pytest_playwright  # noqa: F401 # pyright: ignore[reportUnusedImport, reportMissingTypeStubs]
 
+    except ImportError:
+        raise ImportError(
+            "If you are using pytest to test your app,"
+            " you can install the pytest-playwright shim package with this command:",
+            "\n\n    pip install pytest-playwright",
+        )
+except ImportError:
+    pass
 from . import controls, expect
 
 __all__ = ["expect", "controls"]