JUnit @RepeatedTest Annotation

JUnit is a popular testing framework in the Java ecosystem that simplifies writing and running tests. The @RepeatedTest annotation in JUnit is used to run the same test multiple times. This guide covers the basics of using the @RepeatedTest annotation to write repeated tests in JUnit.

Table of Contents

1. Introduction
2. Steps to Create a JUnit Repeated Test
3. Real-World Use Case
4. Conclusion

Introduction

The @RepeatedTest annotation marks methods that should be executed multiple times. This is useful for tests that need to be run repeatedly to ensure consistency or to perform stress testing.

Steps to Create a JUnit Repeated Test

Step 1: Add Maven Dependency

To use JUnit in your project, you need to add the JUnit dependency to your pom.xml file. Use the latest version of JUnit 5:

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.9.2</version>
    <scope>test</scope>
</dependency>

Step 2: Create the Class to be Tested

Create a Java class with methods that you want to test. For example, a simple Counter class:

public class Counter {
    private int count = 0;

    public int increment() {
        return ++count;
    }

    public int getCount() {
        return count;
    }
}

Step 3: Create the Repeated Test Class

Create a test class in the src/test/java directory. Use the @RepeatedTest annotation to specify the number of repetitions.

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.RepeatedTest;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class CounterTest {
    private Counter counter;

    @BeforeEach
    void setUp() {
        counter = new Counter();
    }

    @RepeatedTest(5)
    void testIncrement() {
        int expected = counter.getCount() + 1;
        int actual = counter.increment();
        assertEquals(expected, actual, "Counter increment should match expected value");
    }
}

In this example, the testIncrement method is annotated with @RepeatedTest(5), which means it will be executed five times. The setUp method is annotated with @BeforeEach to ensure that a new Counter instance is created before each test repetition.

Step 4: Run the Test

You can run the test using your IDE, Maven, or Gradle.

Using an IDE:

Most IDEs, like IntelliJ IDEA and Eclipse, have built-in support for running JUnit tests. Simply right-click on your test class or method and select “Run.”

Using Maven:

If you’re using Maven, you can run your tests with the following command:

mvn test

Using Gradle:

If you’re using Gradle, you can run your tests with the following command:

gradle test

Real-World Use Case

In real-world applications, you may need to run the same test multiple times to ensure consistency or to perform stress testing. For instance, a LoginService class might need to be tested repeatedly to ensure that it handles multiple login attempts correctly.

Create the Class to be Tested

Create a Java class that contains business logic. For example, a LoginService class that processes login attempts:

public class LoginService {
    private int loginAttempts = 0;

    public boolean login(String username, String password) {
        loginAttempts++;
        // Simulate login logic
        return "user".equals(username) && "pass".equals(password);
    }

    public int getLoginAttempts() {
        return loginAttempts;
    }
}

In this class, the login method simulates a login attempt and increments the login attempts counter.

Create the Repeated Test Class

Create a test class for the LoginService in the src/test/java directory. Use the @RepeatedTest annotation to specify the number of repetitions:

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.RepeatedTest;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class LoginServiceTest {
    private LoginService loginService;

    @BeforeEach
    void setUp() {
        loginService = new LoginService();
    }

    @RepeatedTest(5)
    void testLogin() {
        assertTrue(loginService.login("user", "pass"), "Login should be successful");
    }
}

In this test class, the testLogin method is annotated with @RepeatedTest(5), which means it will be executed five times. The setUp method is annotated with @BeforeEach to ensure that a new LoginService instance is created before each test repetition.

Running the Tests

You can run the tests using your IDE, Maven, or Gradle.

Using an IDE:

Most IDEs, like IntelliJ IDEA and Eclipse, have built-in support for running JUnit tests. Simply right-click on your test class or method and select “Run.”

Using Maven:

If you’re using Maven, you can run your tests with the following command:

mvn test

Using Gradle:

If you’re using Gradle, you can run your tests with the following command:

gradle test

Conclusion

The @RepeatedTest annotation in JUnit makes it easy to run the same test multiple times. By using @RepeatedTest, you can ensure that your methods behave consistently across multiple executions and perform stress testing without writing multiple test cases.