dart-generate-test-mocks

Name: dart-generate-test-mocks
Author: flutter

788installs159forks

How to install dart-generate-test-mocks?

flutter/agent-plugins/dart-generate-test-mocks

$npx -y skills add flutter/agent-plugins --skill dart-generate-test-mocks

Installs into the current project.

Summary

Define and generate mock objects for external dependencies using package:mockito and build_runner. Use when unit testing classes that depend on complex external services like APIs or databases.

Files · 1

View on GitHub

SKILL.md

1	# Testing and Mocking Dart Applications
2
3	## Contents
4	- [Structuring Code for Testability](#structuring-code-for-testability)
5	- [Managing Dependencies](#managing-dependencies)
6	- [Generating Mocks](#generating-mocks)
7	- [Implementing Unit Tests](#implementing-unit-tests)
8	- [Workflow: Creating and Running Mocked Tests](#workflow-creating-and-running-mocked-tests)
9	- [Examples](#examples)
10
11	## Structuring Code for Testability
12	Design Dart classes to support dependency injection. Isolate complex external dependencies (like API clients or databases) so they can be replaced with mock objects during testing.
13
14	- Inject external services (e.g., `http.Client`) through class constructors.
15	- Represent URLs strictly as `Uri` objects using `Uri.parse(string)`.
16	- Utilize Dart's object-oriented features (classes, mixins) to define clear interfaces for external interactions.
17
18	## Managing Dependencies
19	Configure the `pubspec.yaml` file with the necessary testing and code generation packages.
20
21	- Add runtime dependencies (e.g., `package:http`) using `dart pub add http`.
22	- Add testing dependencies using `dart pub add dev:test dev:mockito dev:build_runner`.
23	- Import HTTP libraries with a prefix to avoid namespace collisions: `import 'package:http/http.dart' as http;`.
24
25	## Generating Mocks
26	Use `package:mockito` and `build_runner` to automatically generate mock classes for fixed scenarios and behavior verification.
27
28	- Always use the `@GenerateNiceMocks` annotation (preferable to `@GenerateMocks` to avoid missing stub exceptions).
29	- Place the annotation in the test file, passing a list of `MockSpec<Type>()` objects.
30	- Import the generated file using the `.mocks.dart` extension.
31	- Execute `build_runner` to generate the mock files: `dart run build_runner build`.
32
33	## Implementing Unit Tests
34	Isolate the system under test using the generated mock objects. Use `package:test` to structure the test suite.
35
36	- Stubbing: Configure mock behavior before interacting with the system under test.
37	- Use `when(mock.method()).thenReturn(value)` for synchronous methods.
38	- CRITICAL: Always use `thenAnswer((_) async => value)` for methods returning a `Future` or `Stream`. Never use `thenReturn` for asynchronous returns.
39	- Verification: Assert that the system under test interacted with the mock object correctly.
40	- Use `verify(mock.method()).called(1)` to check exact invocation counts.
41	- Use argument matchers like `any`, `anyNamed`, or `captureAny` for flexible verification.
42
43	## Workflow: Creating and Running Mocked Tests
44
45	Use the following checklist to implement and verify mocked unit tests.
46
47	### Task Progress
48	- [ ] 1. Identify the external dependency to mock (e.g., `http.Client`).
49	- [ ] 2. Inject the dependency into the target class constructor.
50	- [ ] 3. Create a test file (e.g., `target_test.dart`) and add `@GenerateNiceMocks([MockSpec<Dependency>()])`.
51	- [ ] 4. Add the `part` or `import` directive for the generated `.mocks.dart` file.
52	- [ ] 5. Run `dart run build_runner build` to generate the mock classes.
53	- [ ] 6. Write the test cases using `group()` and `test()`.
54	- [ ] 7. Stub required behaviors using `when()`.
55	- [ ] 8. Execute the target method.
56	- [ ] 9. Verify interactions using `verify()` and assert outcomes using `expect()`.
57	- [ ] 10. Run the test suite using `dart test`.
58
59	### Feedback Loop: Test Failures
60	If tests fail or `build_runner` encounters errors:
61	1. Run validator: Execute `dart test` or `dart run build_runner build`.
62	2. Review errors: Check for missing stubs, mismatched argument matchers, or syntax errors in the generated files.
63	3. Fix:
64	- If a mock method throws an unexpected null error, ensure you used `@GenerateNiceMocks`.
65	- If an async stub throws an `ArgumentError`, change `thenReturn` to `thenAnswer`.
66	- If `build_runner` fails, ensure the `.mocks.dart` import matches the file name exactly.
67	4. Repeat until all tests pass.
68
69	## Examples
70
71	### High-Fidelity Mocking and Testing Example
72
73	1. System Under Test (`lib/api_service.dart`)
74	```dart
75	import 'dart:convert';
76	import 'package:http/http.dart' as http;
77
78	class ApiService {
79	final http.Client client;
80
81	ApiService(this.client);
82
83	Future<String> fetchData(String urlString) async {
84	final uri = Uri.parse(urlString);
85	final response = await client.get(uri);
86
87	if (response.statusCode == 200) {
88	return jsonDecode(response.body)['data'];
89	} else {
90	throw Exception('Failed to load data');
91	}
92	}
93	}
94	```
95
96	2. Test Implementation (`test/api_service_test.dart`)
97	```dart
98	import 'package:test/test.dart';
99	import 'package:mockito/annotations.dart';
100	import 'package:mockito/mockito.dart';
101	import 'packa

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Type

dart-generate-test-mocks

788installs159forks

View on GitHub

How to install dart-generate-test-mocks?

flutter/agent-plugins/dart-generate-test-mocks

$npx -y skills add flutter/agent-plugins --skill dart-generate-test-mocks

Installs into the current project.

Summary

Define and generate mock objects for external dependencies using package:mockito and build_runner. Use when unit testing classes that depend on complex external services like APIs or databases.

Files · 1

View on GitHub

SKILL.md

1	# Testing and Mocking Dart Applications
2
3	## Contents
4	- [Structuring Code for Testability](#structuring-code-for-testability)
5	- [Managing Dependencies](#managing-dependencies)
6	- [Generating Mocks](#generating-mocks)
7	- [Implementing Unit Tests](#implementing-unit-tests)
8	- [Workflow: Creating and Running Mocked Tests](#workflow-creating-and-running-mocked-tests)
9	- [Examples](#examples)
10
11	## Structuring Code for Testability
12	Design Dart classes to support dependency injection. Isolate complex external dependencies (like API clients or databases) so they can be replaced with mock objects during testing.
13
14	- Inject external services (e.g., `http.Client`) through class constructors.
15	- Represent URLs strictly as `Uri` objects using `Uri.parse(string)`.
16	- Utilize Dart's object-oriented features (classes, mixins) to define clear interfaces for external interactions.
17
18	## Managing Dependencies
19	Configure the `pubspec.yaml` file with the necessary testing and code generation packages.
20
21	- Add runtime dependencies (e.g., `package:http`) using `dart pub add http`.
22	- Add testing dependencies using `dart pub add dev:test dev:mockito dev:build_runner`.
23	- Import HTTP libraries with a prefix to avoid namespace collisions: `import 'package:http/http.dart' as http;`.
24
25	## Generating Mocks
26	Use `package:mockito` and `build_runner` to automatically generate mock classes for fixed scenarios and behavior verification.
27
28	- Always use the `@GenerateNiceMocks` annotation (preferable to `@GenerateMocks` to avoid missing stub exceptions).
29	- Place the annotation in the test file, passing a list of `MockSpec<Type>()` objects.
30	- Import the generated file using the `.mocks.dart` extension.
31	- Execute `build_runner` to generate the mock files: `dart run build_runner build`.
32
33	## Implementing Unit Tests
34	Isolate the system under test using the generated mock objects. Use `package:test` to structure the test suite.
35
36	- Stubbing: Configure mock behavior before interacting with the system under test.
37	- Use `when(mock.method()).thenReturn(value)` for synchronous methods.
38	- CRITICAL: Always use `thenAnswer((_) async => value)` for methods returning a `Future` or `Stream`. Never use `thenReturn` for asynchronous returns.
39	- Verification: Assert that the system under test interacted with the mock object correctly.
40	- Use `verify(mock.method()).called(1)` to check exact invocation counts.
41	- Use argument matchers like `any`, `anyNamed`, or `captureAny` for flexible verification.
42
43	## Workflow: Creating and Running Mocked Tests
44
45	Use the following checklist to implement and verify mocked unit tests.
46
47	### Task Progress
48	- [ ] 1. Identify the external dependency to mock (e.g., `http.Client`).
49	- [ ] 2. Inject the dependency into the target class constructor.
50	- [ ] 3. Create a test file (e.g., `target_test.dart`) and add `@GenerateNiceMocks([MockSpec<Dependency>()])`.
51	- [ ] 4. Add the `part` or `import` directive for the generated `.mocks.dart` file.
52	- [ ] 5. Run `dart run build_runner build` to generate the mock classes.
53	- [ ] 6. Write the test cases using `group()` and `test()`.
54	- [ ] 7. Stub required behaviors using `when()`.
55	- [ ] 8. Execute the target method.
56	- [ ] 9. Verify interactions using `verify()` and assert outcomes using `expect()`.
57	- [ ] 10. Run the test suite using `dart test`.
58
59	### Feedback Loop: Test Failures
60	If tests fail or `build_runner` encounters errors:
61	1. Run validator: Execute `dart test` or `dart run build_runner build`.
62	2. Review errors: Check for missing stubs, mismatched argument matchers, or syntax errors in the generated files.
63	3. Fix:
64	- If a mock method throws an unexpected null error, ensure you used `@GenerateNiceMocks`.
65	- If an async stub throws an `ArgumentError`, change `thenReturn` to `thenAnswer`.
66	- If `build_runner` fails, ensure the `.mocks.dart` import matches the file name exactly.
67	4. Repeat until all tests pass.
68
69	## Examples
70
71	### High-Fidelity Mocking and Testing Example
72
73	1. System Under Test (`lib/api_service.dart`)
74	```dart
75	import 'dart:convert';
76	import 'package:http/http.dart' as http;
77
78	class ApiService {
79	final http.Client client;
80
81	ApiService(this.client);
82
83	Future<String> fetchData(String urlString) async {
84	final uri = Uri.parse(urlString);
85	final response = await client.get(uri);
86
87	if (response.statusCode == 200) {
88	return jsonDecode(response.body)['data'];
89	} else {
90	throw Exception('Failed to load data');
91	}
92	}
93	}
94	```
95
96	2. Test Implementation (`test/api_service_test.dart`)
97	```dart
98	import 'package:test/test.dart';
99	import 'package:mockito/annotations.dart';
100	import 'package:mockito/mockito.dart';
101	import 'packa

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Type