junit
Provides comprehensive guidance for JUnit testing framework including test annotations, assertions, test lifecycle, and best practices. Use when the user asks about JUnit, needs to write Java unit tests, use JUnit annotations, or configure JUnit for Java projects.
- Installs
- 117
- Last 24h
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- Security
- Not audited
Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/partme-ai/full-stack-skills --skill junit- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads junit automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
When to use this skill
Use this skill whenever the user wants to:
- Write Java or Kotlin unit tests with JUnit 4 or JUnit 5 (Jupiter)
- Use annotations (@Test, @BeforeEach, @AfterEach, @ParameterizedTest)
- Apply assertions (assertEquals, assertThrows, assertAll)
- Integrate with Mockito or AssertJ for mocking and fluent assertions
- Configure test execution with Maven Surefire or Gradle
How to use this skill
Workflow
- Write test classes and methods annotated with
@Test - Set up and tear down test state with lifecycle annotations
- Use assertions to verify expected behavior
- Mock dependencies with Mockito for isolated unit tests
1. Basic JUnit 5 Test
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
class CalculatorTest {
@Test
void shouldAddTwoNumbers() {
Calculator calc = new Calculator();
assertEquals(5, calc.add(2, 3));
}
@Test
void shouldThrowOnDivideByZero() {
Calculator calc = new Calculator();
assertThrows(ArithmeticException.class, () -> calc.divide(1, 0));
}
}
2. Lifecycle Annotations
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.AfterEach;
class UserServiceTest {
private UserService userService;
@BeforeEach
void setUp() {
userService = new UserService(new InMemoryUserRepository());
}
@AfterEach
void tearDown() {
// Clean up resources
}
}
3. Parameterized Tests
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;
class StringTest {
@ParameterizedTest
@CsvSource({"hello,5", "'',0", "junit,5"})
void shouldReturnCorrectLength(String input, int expected) {
assertEquals(expected, input.length());
}
}
4. Mocking with Mockito
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;
import static org.mockito.Mockito.*;
@ExtendWith(MockitoExtension.class)
class OrderServiceTest {
@Mock private OrderRepository orderRepository;
@InjectMocks private OrderService orderService;
@Test
void shouldSaveOrder() {
Order order = new Order("item-1", 2);
orderService.placeOrder(order);
verify(orderRepository).save(order);
}
}
5. Running Tests
# Maven
mvn test
# Gradle
gradle test
# With coverage (JaCoCo)
mvn test jacoco:report
Best Practices
- Keep tests independent and repeatable; avoid dependencies on execution order or external services
- Use Mockito to isolate the unit under test from its dependencies
- Name tests descriptively (e.g.,
shouldReturnEmptyListWhenNoUsersExist) - Balance coverage with test speed; run full suite in CI
- Use
@Nestedclasses to group related test cases
Resources
- JUnit 5 User Guide: https://junit.org/junit5/docs/current/user-guide/
- Mockito: https://site.mockito.org/
- AssertJ: https://assertj.github.io/doc/
Keywords
junit, JUnit 5, JUnit Jupiter, unit testing, Java, Kotlin, assertions, Mockito, parameterized tests, BeforeEach, AfterEach, test lifecycle
FAQ
What does the junit skill do?
Provides comprehensive guidance for JUnit testing framework including test annotations, assertions, test lifecycle, and best practices. Use when the user asks about JUnit, needs to write Java unit tests, use JUnit annotations, or configure JUnit for Java projects.
How do I install junit?
Run npx skills add https://github.com/partme-ai/full-stack-skills --skill junit in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/junit/ (personal) or .claude/skills/junit/ (project).
Which AI agents can use junit?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is junit safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains junit?
It is published by partme-ai in partme-ai/full-stack-skills. It has 117 recorded installs.
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