Add void return on group callback (#2604)
This type influences type inference and this change can impact what
static diagnostics apply, but is not breaking at the language level.
Currently the callbacks to `test` are left as `FutureOr<dynamic>` for
now, the ecosystem impact may be larger.
Tightening the type on group internally catches some callbacks written
as `() => {test(...)}` and surfaces a diagnostic. This was low impact on
the internal test corpus.
Welcome! package:test is the standard testing library for Dart and Flutter. If you have questions about Dart testing, please see the docs for package:test. package:test_api and package:test_core are implementation details and generally not user-facing.
package:checks is a relatively new library for expressing test expectations. It's a more modern version of package:matcher and features a literate API.
| Package | Description | Issues | Version |
|---|---|---|---|
| checks | A framework for checking values against expectations and building custom expectations. |  |  |
| fake_async | Fake asynchronous events such as timers and microtasks for deterministic testing. | |  |
| matcher | Support for specifying test expectations via an extensible Matcher class. Also includes a number of built-in Matcher implementations for common cases. | |  |
| test | A full featured library for writing and running Dart tests across platforms. | |  |
| test_api | The user facing API for structuring Dart tests and checking expectations. |  | |
| test_core | A basic library for writing tests and running them on the VM. |  | |
| test_descriptor | An API for defining and verifying files and directory structures. | |  |
| test_process | Test processes: starting; validating stdout and stderr; checking exit code. | |  |