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New Annotations in JUnit 5

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JUnit 5 introduced several new annotations that enhance the flexibility and functionality of writing tests. These annotations provide more control over test execution and allow for more expressive and maintainable test code. In this section, we will explore these new annotations, their purposes, and how to use them effectively.

  1. @Test

The @Test annotation is used to denote a method as a test method. This is similar to JUnit 4, but JUnit 5's @Test is part of the org.junit.jupiter.api package.

import org.junit.jupiter.api.Test;

public class MyTests {
    @Test
    void testMethod() {
        // Test logic here
    }
}

  1. @DisplayName

The @DisplayName annotation allows you to provide a custom name for your test methods. This can make your test reports more readable and descriptive.

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

public class MyTests {
    @Test
    @DisplayName("Test addition of two numbers")
    void testAddition() {
        // Test logic here
    }
}

  1. @BeforeEach and @AfterEach

These annotations are used to specify methods that should be executed before and after each test method, respectively. They replace JUnit 4's @Before and @After.

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;

public class MyTests {
    @BeforeEach
    void setUp() {
        // Initialization logic here
    }

    @AfterEach
    void tearDown() {
        // Cleanup logic here
    }

    @Test
    void testMethod() {
        // Test logic here
    }
}

  1. @BeforeAll and @AfterAll

These annotations are used to specify methods that should be executed once before all tests and once after all tests, respectively. They replace JUnit 4's @BeforeClass and @AfterClass. Methods annotated with @BeforeAll and @AfterAll must be static.

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.Test;

public class MyTests {
    @BeforeAll
    static void initAll() {
        // Initialization logic here
    }

    @AfterAll
    static void tearDownAll() {
        // Cleanup logic here
    }

    @Test
    void testMethod() {
        // Test logic here
    }
}

  1. @Nested

The @Nested annotation allows you to create nested test classes, which can help organize tests into logical groups. Nested test classes can have their own lifecycle methods.

import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;

public class MyTests {
    @Nested
    class InnerTests {
        @Test
        void innerTestMethod() {
            // Test logic here
        }
    }
}

  1. @Tag

The @Tag annotation is used to tag test methods or classes. This can be useful for filtering tests during execution.

import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;

public class MyTests {
    @Test
    @Tag("fast")
    void fastTest() {
        // Fast test logic here
    }

    @Test
    @Tag("slow")
    void slowTest() {
        // Slow test logic here
    }
}

  1. @Disabled

The @Disabled annotation is used to disable a test method or class. This is similar to JUnit 4's @Ignore.

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;

public class MyTests {
    @Test
    @Disabled("Disabled until bug #123 is fixed")
    void disabledTest() {
        // This test will not run
    }
}

  1. @RepeatedTest

The @RepeatedTest annotation is used to run a test multiple times. This can be useful for testing idempotency or performance.

import org.junit.jupiter.api.RepeatedTest;

public class MyTests {
    @RepeatedTest(5)
    void repeatedTest() {
        // This test will run 5 times
    }
}

  1. @ParameterizedTest

The @ParameterizedTest annotation is used to run a test with different parameters. This is a powerful feature for testing with multiple sets of data.

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

public class MyTests {
    @ParameterizedTest
    @ValueSource(strings = {"Hello", "JUnit"})
    void parameterizedTest(String word) {
        // This test will run with "Hello" and "JUnit"
    }
}

Summary

JUnit 5 introduces several new annotations that provide more flexibility and control over test execution. These annotations help in writing more expressive, maintainable, and organized test code. Understanding and utilizing these annotations effectively can significantly improve your testing practices.

In the next topic, we will explore how to migrate from JUnit 4 to JUnit 5, ensuring a smooth transition and leveraging the new features provided by JUnit 5.

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