anchor.diff:        // Only execute the check below once. `Invoker.current` may look like a
         // cheap getter, but it involves Zones and casting.
         _testApiMismatchHasBeenChecked = true;
  -      _checkTestApiMismatch();
       }
       expect(callCount, wrapMatcher(matcher),
           reason: 'Unexpected number of calls');
  
positive.code: 
    VerificationResult._(this.callCount, this._captured);
  
    /// Check for a version incompatibility between mockito, test, and test_api.
    ///
    /// This incompatibility results in an inscrutible error for users. Catching
    /// it here allows us to give some steps to fix.
    // TODO(srawlins): Remove this when we don't need to check for an
    // incompatiblity between test_api and test any more.
    // https://github.com/dart-lang/mockito/issues/175
    void _checkTestApiMismatch() {
      try {
        Invoker.current;
      } on TypeError catch (e) {
        if (!e
            .toString()
            .contains("type 'Invoker' is not a subtype of type 'Invoker'")) {
          // Hmm. This is a different CastError from the one we're trying to
          // protect against. Let it go.
          return;
        }
        print('Error: Package incompatibility between mockito, test, and '
            'test_api packages:');
        print('');
        print('* mockito ^4.0.0 is incompatible with test <1.4.0');
        print('* mockito <4.0.0 is incompatible with test ^1.4.0');
        print('');
        print('As mockito does not have a dependency on the test package, '
            'nothing stopped you from landing in this situation. :( '
            'Apologies.');
        print('');
        print('To fix: bump your dependency on the test package to something '
            'like: ^1.4.0, or downgrade your dependency on mockito to something '
            'like: ^3.0.0');
        rethrow;
      }
    }
  
    /// Assert that the number of calls matches [matcher].
    ///
    /// Examples:
  
negative.code: import 'package:test_api/fake.dart';
  // ignore: deprecated_member_use
  import 'package:test_api/test_api.dart';
  
  /// Whether a [when] call is "in progress."
  ///
  