Name: dart-add-unit-test
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Testing Dart and Flutter Applications
Contents
Structuring Test Files
Writing Tests
Executing Tests
Test Implementation Workflow
Examples
Structuring Test Files
Organize test files to mirror the
lib
directory structure to maintain predictability.
Place all test code within the
test
directory at the root of the package.
Append
_test.dart
to the end of all test file names (e.g.,
lib/src/utils.dart
should be tested in
test/src/utils_test.dart
).
If writing integration tests, place them in an
integration_test
directory at the root of the package.
Writing Tests
Utilize
package:test
as the standard testing library for Dart applications.
Import
package:test/test.dart
(or
package:flutter_test/flutter_test.dart
for Flutter).
Group related tests using the
group()
function to provide shared context.
Define individual test cases using the
test()
function.
Validate outcomes using the
expect()
function alongside matchers (e.g.,
equals()
,
isTrue
,
throwsA()
).
Write asynchronous tests using standard
async
/
await
syntax. The test runner automatically waits for the
Future
to complete.
Manage test setup and teardown using
setUp()
and
tearDown()
callbacks.
If testing code that relies on dependency injection, use
package:mockito
alongside
package:test
to generate mock objects, configure fixed scenarios, and verify interactions.
Executing Tests
Select the appropriate test runner based on the project type and test location.
If working on a pure Dart project, execute tests using the
dart test
command.
If working on a Flutter project, execute tests using the
flutter test
command.
If running integration tests, explicitly specify the directory path, as the default runner ignores it:
dart test integration_test
or
flutter test integration_test
.
Test Implementation Workflow
Follow this sequential workflow when implementing new test suites. Copy the checklist to track your progress.
Task Progress
1. Create the test file in the
test/
directory, ensuring the
_test.dart
suffix.
2. Import
package:test/test.dart
and the target library.
3. Define a
main()
function.
4. Initialize shared resources or mocks using
setUp()
.
5. Write
test()
cases grouped by functionality using
group()
.
6. Execute the test suite using the appropriate CLI command.
7.
Feedback Loop: Run test -> Review stack trace for failures -> Fix implementation or assertions -> Re-run until passing. Examples Standard Unit Test Suite Demonstrates grouping, setup, synchronous, and asynchronous testing. import 'package:test/test.dart' ; import 'package:my_package/calculator.dart' ; void main ( ) { group ( 'Calculator' , ( ) { late Calculator calc ; setUp ( ( ) { calc = Calculator ( ) ; } ) ; test ( 'adds two numbers correctly' , ( ) { expect ( calc . add ( 2 , 3 ) , equals ( 5 ) ) ; } ) ; test ( 'handles asynchronous operations' , ( ) async { final result = await calc . fetchRemoteValue ( ) ; expect ( result , isNotNull ) ; expect ( result , greaterThan ( 0 ) ) ; } ) ; } ) ; } Mocking with Mockito Demonstrates configuring a mock object for dependency injection testing. import 'package:test/test.dart' ; import 'package:mockito/mockito.dart' ; import 'package:mockito/annotations.dart' ; import 'package:my_package/api_client.dart' ; import 'package:my_package/data_service.dart' ; // Generate the mock using build_runner: dart run build_runner build @GenerateNiceMocks ( [ MockSpec < ApiClient

( ) ] ) import 'data_service_test.mocks.dart' ; void main ( ) { group ( 'DataService' , ( ) { late MockApiClient mockApiClient ; late DataService dataService ; setUp ( ( ) { mockApiClient = MockApiClient ( ) ; dataService = DataService ( apiClient : mockApiClient ) ; } ) ; test ( 'returns parsed data on successful API call' , ( ) async { // Configure the mock when ( mockApiClient . get ( '/data' ) ) . thenAnswer ( ( _ ) async =

'{"id": 1}' ) ; // Execute the system under test final result = await dataService . fetchData ( ) ; // Verify outcomes and interactions expect ( result . id , equals ( 1 ) ) ; verify ( mockApiClient . get ( '/data' ) ) . called ( 1 ) ; } ) ; } ) ; }

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