重置 TestTextInput 状态

Summary

The state of a TestTextInput instance, a stub for the system’s onscreen keyboard, is now reset between tests.

Context

The Flutter test framework uses a class called TestTextInput to track and manipulate editing state in a widgets test. Individual tests can make calls that modify the internal state of this object, sometimes indirectly (such as by setting their own handlers on SystemChannels.textInput). Subsequent tests might then check the state of WidgetTester.testTextInput and get unexpected values.

Description of change

The state of WidgetTester.testTextInput is now reset before running a testWidgets test.

Migration guide

Tests that relied on dirty state from a previously run test must be updated. For example, the following test, from packages/flutter/test/material/text_field_test.dart in the 'Controller can update server' test, previously passed because of a combination of dirty state from previous tests and a failure to actually set state in cases where it should have been set.

Code before migration:

In a widgetsTest, before actually changing text on a text editing widget, this call might have succeeded:

    expect(tester.testTextInput.editingState['text'], isEmpty);

Code after migration:

Either remove the call entirely, or consider using the following to assert that the state hasn’t been modified yet:

    expect(tester.testTextInput.editingState, isNull);

Timeline

Landed in version: 1.16.3
In stable release: 1.17

References

API documentation:

Relevant issue:

Relevant PR: