Test suites with @Suite in JUnit - Build an Automation Script

Create and run a JUnit test suite using @Suite

Preconditions (2)

Step 1: Create a new Java class named AllTestsSuite

Step 2: Annotate the class with @Suite and @SelectClasses

Step 3: Include the two existing test classes in @SelectClasses

Step 4: Run the AllTestsSuite class as a JUnit test

Step 5: Observe that all tests from the included classes run

✅ Expected Result: All test methods from the specified test classes run successfully when running the suite class

Automation Requirements - JUnit 5

Assertions Needed:

Verify that all tests from included classes are executed

Verify that the suite class runs without errors

Best Practices:

Use @Suite and @SelectClasses annotations properly

Keep test classes independent and focused

Name the suite class clearly to indicate it is a test suite

Automated Solution

JUnit

import org.junit.platform.suite.api.SelectClasses;
import org.junit.platform.suite.api.Suite;

@Suite
@SelectClasses({CalculatorTest.class, StringUtilsTest.class})
public class AllTestsSuite {
    // This class remains empty, it is used only as a holder for the above annotations
}

// Example test class 1
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Test;

public class CalculatorTest {
    @Test
    void addition() {
        assertEquals(5, 2 + 3);
    }
}

// Example test class 2
import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;

public class StringUtilsTest {
    @Test
    void isEmptyReturnsTrueForEmptyString() {
        assertTrue("".isEmpty());
    }
}

The AllTestsSuite class is annotated with @Suite and @SelectClasses to specify which test classes to run together.

The suite class itself has no methods; it just groups the tests.

Two example test classes, CalculatorTest and StringUtilsTest, each have simple test methods with assertions.

Running AllTestsSuite will run all tests from both classes, verifying the suite setup works.

Common Mistakes - 3 Pitfalls

Not annotating the suite class with @Suite

{'mistake': 'Using @RunWith(Suite.class) from JUnit 4 in JUnit 5 projects', 'why_bad': 'JUnit 5 uses different annotations and runners; mixing versions causes tests not to run.', 'correct_approach': "Use JUnit 5's @Suite and @SelectClasses annotations for test suites."}

Including test classes that do not have any test methods

Bonus Challenge

Add a third test class to the suite and verify all three classes run together

Show Hint

Practice

1. What is the main purpose of using @Suite in JUnit testing?

easy

A. To group multiple test classes to run together as one unit

B. To mark a method as a test case

C. To ignore a test class during execution

D. To specify the order of test methods within a class

Solution

1. Step 1: Understand the role of @Suite

   @Suite is an annotation used to create a test suite that groups multiple test classes.

2. Step 2: Compare with other annotations

   @Test marks methods as tests, @Ignore skips tests, and ordering is handled differently, so these do not match @Suite's purpose.

3. Final Answer:

   To group multiple test classes to run together as one unit -> Option A

4. Quick Check:

   @Suite groups classes = B [OK]

Hint: Remember: @Suite groups classes, not individual tests [OK]

Common Mistakes:

• Confusing @Suite with @Test annotation
• Thinking @Suite controls test method order
• Assuming @Suite skips tests

2. Which of the following is the correct way to declare a JUnit 5 test suite using @Suite and @SelectClasses?

easy

A. @Suite
@SelectClasses({TestA.class, TestB.class})
public class AllTests {}

B. @SuiteClasses({TestA.class, TestB.class})
public class AllTests {}

C. @RunWith(Suite.class)
@SuiteClasses({TestA.class, TestB.class})
public class AllTests {}

D. @TestSuite
@SelectClasses({TestA.class, TestB.class})
public class AllTests {}

Solution

1. Step 1: Identify JUnit 5 suite syntax

   JUnit 5 uses @Suite and @SelectClasses annotations together to define a suite.

2. Step 2: Check other options for JUnit 4 syntax or invalid annotations

   @RunWith and @SuiteClasses are JUnit 4 style; @TestSuite is invalid.

3. Final Answer:

   @Suite @SelectClasses({TestA.class, TestB.class}) public class AllTests {} -> Option A

4. Quick Check:

   JUnit 5 suite = @Suite + @SelectClasses [OK]

Hint: JUnit 5 suites use @Suite and @SelectClasses together [OK]

Common Mistakes:

• Using JUnit 4 annotations in JUnit 5 code
• Misspelling @SelectClasses
• Omitting the public class declaration

3. Given the following test suite code, what will happen when you run AllTests?

@Suite
@SelectClasses({TestOne.class, TestTwo.class})
public class AllTests {}

medium

A. Only TestTwo's tests will run

B. Both TestOne and TestTwo classes will run all their test methods

C. Only TestOne's tests will run

D. No tests will run because the suite class is empty

Solution

1. Step 1: Understand @SelectClasses effect

   @SelectClasses lists test classes to include in the suite; all their tests run.

2. Step 2: Confirm suite class content is irrelevant

   The suite class itself is a container; it does not need test methods to run included tests.

3. Final Answer:

   Both TestOne and TestTwo classes will run all their test methods -> Option B

4. Quick Check:

   @SelectClasses runs all listed classes [OK]

Hint: Suite runs all classes listed in @SelectClasses [OK]

Common Mistakes:

• Thinking suite class must have test methods
• Assuming only first class runs
• Believing empty suite class means no tests

4. Identify the error in this JUnit 5 test suite declaration:

@Suite
@SelectClasses({TestA.class, TestB.class})
public void AllTests() {}

medium

A. Suite class must extend a base test class

B. Missing @Test annotation on AllTests method

C. @SelectClasses cannot include multiple classes

D. Suite class should not be a method; it must be a class declaration

Solution

1. Step 1: Check the suite declaration syntax

   The suite must be a class, not a method. Here, 'public void AllTests()' is a method.

2. Step 2: Validate other options

   @Test is not needed on suite, @SelectClasses supports multiple classes, and no inheritance is required.

3. Final Answer:

   Suite class should not be a method; it must be a class declaration -> Option D

4. Quick Check:

   Suite must be a class, not a method [OK]

Hint: Suite must be a class, not a method [OK]

Common Mistakes:

• Writing suite as a method instead of a class
• Adding unnecessary @Test to suite
• Thinking suite must extend another class

5. You want to create a test suite that runs LoginTests, PaymentTests, and LogoutTests classes. Which of the following is the best way to write this suite in JUnit 5?

hard

A. @Suite
@SelectPackages({"com.example.tests"})
public class FullSuite {}

B. @SuiteClasses({LoginTests.class, PaymentTests.class, LogoutTests.class})
public class FullSuite {}

C. @Suite
@SelectClasses({LoginTests.class, PaymentTests.class, LogoutTests.class})
public class FullSuite {}

D. @RunWith(Suite.class)
@SelectClasses({LoginTests.class, PaymentTests.class, LogoutTests.class})
public class FullSuite {}

Solution

1. Step 1: Use correct JUnit 5 annotations

   JUnit 5 uses @Suite and @SelectClasses to specify test classes in a suite.

2. Step 2: Evaluate other options

   @SuiteClasses and @RunWith are JUnit 4 style; @SelectPackages is for packages, not specific classes.

3. Final Answer:

   @Suite @SelectClasses({LoginTests.class, PaymentTests.class, LogoutTests.class}) public class FullSuite {} -> Option C

4. Quick Check:

   JUnit 5 suite = @Suite + @SelectClasses [OK]

Hint: Use @Suite with @SelectClasses listing all test classes [OK]

Common Mistakes:

• Mixing JUnit 4 and 5 annotations
• Using @SelectPackages when classes are needed
• Omitting public class declaration