Test suites with @Suite in JUnit

Introduction

Test suites help you run many test classes together in one go. This saves time and keeps tests organized.

When you want to run all tests for a feature at once.

When you have multiple test classes for different parts of your app and want to run them together.

When you want to group slow tests separately from fast tests.

When you want to run all tests before a release to check everything works.

When you want to organize tests by modules or layers in your project.

Syntax

JUnit

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

@Suite
@SelectClasses({TestClass1.class, TestClass2.class})
public class MyTestSuite {
}

The @Suite annotation marks the class as a test suite.

@SelectClasses lists the test classes to run in this suite.

Examples

This suite runs tests from LoginTests and SignupTests classes together.

JUnit

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

@Suite
@SelectClasses({LoginTests.class, SignupTests.class})
public class UserTestsSuite {
}

This suite runs only the DatabaseTests class.

JUnit

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

@Suite
@SelectClasses({DatabaseTests.class})
public class DatabaseTestSuite {
}

Sample Program

This example has two test classes each with one simple test. The suite MyTestSuite runs both classes together.

JUnit

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

public class TestClass1 {
    @Test
    void testOne() {
        assertTrue(1 + 1 == 2);
    }
}

public class TestClass2 {
    @Test
    void testTwo() {
        assertTrue("hello".startsWith("h"));
    }
}

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

@Suite
@SelectClasses({TestClass1.class, TestClass2.class})
public class MyTestSuite {
}

Important Notes

Test classes included in the suite must be public and have valid test methods.

You can add more test classes by listing them in @SelectClasses.

Use your IDE or build tool to run the suite class as a JUnit test.

Summary

Test suites group multiple test classes to run together.

Use @Suite and @SelectClasses annotations to create a suite.

Suites help organize and save time when running many tests.

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