TestWidgetsFlutterBinding class abstract

Base class for bindings used by widgets library tests.

The ensureInitialized method creates (if necessary) and returns an instance of the appropriate subclass. (If one is already created, it returns that one, even if it's not the one that it would normally create. This allows tests to force the use of LiveTestWidgetsFlutterBinding even in a normal unit test environment, e.g. to test that binding.)

When using these bindings, certain features are disabled. For example, timeDilation is reset to 1.0 on initialization.

In non-browser tests, the binding overrides HttpClient creation with a fake client that always returns a status code of 400. This is to prevent tests from making network calls, which could introduce flakiness. A test that actually needs to make a network call should provide its own HttpClient to the code making the call, so that it can appropriately mock or fake responses.

Coordinate spaces

TestWidgetsFlutterBinding might be run on devices of different screen sizes, while the testing widget is still told the same size to ensure consistent results. Consequently, code that deals with positions (such as pointer events or painting) must distinguish between two coordinate spaces:

• The local coordinate space is the one used by the testing widget (typically an 800 by 600 window, but can be altered by setSurfaceSize).
• The global coordinate space is the one used by the device.

Positions can be transformed between coordinate spaces with localToGlobal and globalToLocal.