@Tag for categorization in JUnit - Build an Automation Script

Verify test execution filtering using @Tag annotation

Preconditions (2)

Step 1: Run tests with the tag filter set to 'fast'

Step 2: Observe which tests are executed

Step 3: Run tests with the tag filter set to 'slow'

Step 4: Observe which tests are executed

✅ Expected Result: Only tests with the specified tag are executed in each run

Automation Requirements - JUnit 5

Assertions Needed:

Verify that tests with the selected tag run

Verify that tests without the selected tag do not run

Best Practices:

Use @Tag annotation on test methods for categorization

Use JUnit 5's built-in tag filtering to run specific groups

Keep test methods independent and clearly tagged

Automated Solution

JUnit

import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class TagExampleTest {

    @Test
    @Tag("fast")
    void fastTest() {
        assertTrue(true, "Fast test should always pass");
    }

    @Test
    @Tag("slow")
    void slowTest() {
        assertTrue(true, "Slow test should always pass");
    }

    @Test
    void untaggedTest() {
        assertTrue(true, "Untagged test should always pass");
    }
}

/*
To run tests with tag 'fast', use:

mvn test -Dgroups=fast

or configure your IDE or build tool to include only @Tag("fast") tests.

This example shows how to categorize tests and run them selectively.
*/

This code defines three test methods: one tagged as fast, one as slow, and one without any tag.

The @Tag annotation categorizes tests. You can run tests filtered by these tags using your build tool or IDE settings.

Assertions simply verify the tests run and pass. The untagged test runs unless filtered out.

This setup helps organize tests by speed or type, making test runs faster and more focused.

Common Mistakes - 3 Pitfalls

Not using @Tag annotation on test methods

{'mistake': "Using the same tag name inconsistently (e.g., 'Fast' vs 'fast')", 'why_bad': 'Tag filtering is case-sensitive, so inconsistent tags cause unexpected test runs.', 'correct_approach': 'Use consistent lowercase tag names throughout the project.'}

Trying to filter tests without configuring the build tool or IDE

Bonus Challenge

Add tests with multiple tags and run tests that match any of the tags

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