[matcher] Add type check in pairwiseCompare (#2596)
Closes #2454
Currently a failure from the cast causes a failure output including:
Which: has <null> which is not <null> at index null
Fill in the missing info by adding an explicit type check instead of an
unchecked cast before passing to the comparison callback. Elements with
mismatched type are treated identically to those which fail the
comparison, but should be clear to a reader of the failure.
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. | |  |