A Dart package that makes testing blocs and cubits easy. Built to work with bloc and mocktail.
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Create a Mock
import 'package:bloc_test/bloc_test.dart';
class MockCounterBloc extends MockBloc<CounterEvent, int> implements CounterBloc {}
class MockCounterCubit extends MockCubit<int> implements CounterCubit {}
Stub the State Stream
whenListen creates a stub response for the listen
method on a bloc or cubit. Use whenListen
if you want to return a canned Stream
of states. whenListen
also handles stubbing the state
to stay in sync with the emitted state.
// Create a mock instance
final counterBloc = MockCounterBloc();
// Stub the state stream
whenListen(
counterBloc,
Stream.fromIterable([0, 1, 2, 3]),
initialState: 0,
);
// Assert that the initial state is correct.
expect(counterBloc.state, equals(0));
// Assert that the stubbed stream is emitted.
await expectLater(counterBloc.stream, emitsInOrder(<int>[0, 1, 2, 3]));
// Assert that the current state is in sync with the stubbed stream.
expect(counterBloc.state, equals(3));
Unit Test with blocTest
blocTest creates a new bloc
-specific test case with the given description
.
blocTest
will handle asserting that the bloc
emits the expect
ed states (in order) after act
is executed. blocTest
also handles ensuring that no additional states are emitted by closing the bloc
stream before evaluating the expect
ation.
setUp
is optional and should be used to set up any dependencies prior to initializing the bloc
under test. setUp
should be used to set up state necessary for a particular test case. For common set up code, prefer to use setUp
from package:test/test.dart
.
build
should construct and return the bloc
under test.
seed
is an optional Function
that returns a state which will be used to seed the bloc
before act
is called.
act
is an optional callback which will be invoked with the bloc
under test and should be used to interact with the bloc
.
skip
is an optional int
which can be used to skip any number of states. skip
defaults to 0.
wait
is an optional Duration
which can be used to wait for async operations within the bloc
under test such as debounceTime
.
expect
is an optional Function
that returns a Matcher
which the bloc
under test is expected to emit after act
is executed.
verify
is an optional callback which is invoked after expect
and can be used for additional verification/assertions. verify
is called with the bloc
returned by build
.
errors
is an optional Function
that returns a Matcher
which the bloc
under test is expected to throw after act
is executed.
tearDown
is optional and can be used to execute any code after the test has run. tearDown
should be used to clean up after a particular test case. For common tear down code, prefer to use tearDown
from package:test/test.dart
.
tags
is optional and if it is passed, it declares user-defined tags that are applied to the test. These tags can be used to select or skip the test on the command line, or to do bulk test configuration.
group('CounterBloc', () {
blocTest(
'emits [] when nothing is added',
build: () => CounterBloc(),
expect: () => [],
);
blocTest(
'emits [1] when CounterIncrementPressed is added',
build: () => CounterBloc(),
act: (bloc) => bloc.add(CounterIncrementPressed()),
expect: () => [1],
);
});
blocTest
can optionally be used with a seeded state.
blocTest(
'emits [10] when seeded with 9',
build: () => CounterBloc(),
seed: () => 9,
act: (bloc) => bloc.add(CounterIncrementPressed()),
expect: () => [10],
);
blocTest
can also be used to skip
any number of emitted states before asserting against the expected states. The default value is 0.
blocTest(
'emits [2] when CounterIncrementPressed is added twice',
build: () => CounterBloc(),
act: (bloc) => bloc..add(CounterIncrementPressed())..add(CounterIncrementPressed()),
skip: 1,
expect: () => [2],
);
blocTest
can also be used to wait for async operations like debounceTime
by providing a Duration
to wait
.
blocTest(
'emits [MyState] when MyEvent is added',
build: () => MyBloc(),
act: (bloc) => bloc.add(MyEvent()),
wait: const Duration(milliseconds: 300),
expect: () => [isA<MyState>()],
);
blocTest
can also be used to verify
internal bloc functionality.
blocTest(
'emits [MyState] when MyEvent is added',
build: () => MyBloc(),
act: (bloc) => bloc.add(MyEvent()),
expect: () => [isA<MyState>()],
verify: (_) {
verify(() => repository.someMethod(any())).called(1);
}
);
blocTest
can also be used to expect that exceptions have been thrown.
blocTest(
'throws Exception when null is added',
build: () => MyBloc(),
act: (bloc) => bloc.add(null),
errors: () => [isA<Exception>()]
);
Note: when using blocTest
with state classes which don't override ==
and hashCode
you can provide an Iterable
of matchers instead of explicit state instances.
blocTest(
'emits [MyState] when MyEvent is added',
build: () => MyBloc(),
act: (bloc) => bloc.add(MyEvent()),
expect: () => [isA<MyState>()],
);
Dart Versions
- Dart 2: >= 2.12
Maintainers
Libraries
- bloc_test
- A testing library which makes it easy to test blocs.