What is a test suite in JUnit, and how do you create it?

Question

Accepted Answer

A test suite groups multiple test classes together so they can be executed as a single run, useful for organizing related tests or running a full regression pass.

Key Points:
• In JUnit 4, create a suite class annotated with @RunWith(Suite.class) and @Suite.SuiteClasses({TestA.class, TestB.class}).
• The suite class itself typically has no test methods - it just declares which classes to include.
• In JUnit 5, suites are built with the junit-platform-suite module using @Suite and @SelectClasses or @SelectPackages.
• Test suites are useful for grouping tests by feature area or for defining a smoke-test subset versus a full regression subset.
• Most modern build tools (Maven Surefire/Failsafe, Gradle) can already run all tests in a module without a suite, making explicit suites less essential than they once were.

Example:
A RegressionSuite class listing UserServiceTest, OrderServiceTest, and PaymentServiceTest lets you run all three together with a single test execution.

Code Example:
```
@RunWith(Suite.class)
@Suite.SuiteClasses({
    UserServiceTest.class,
    OrderServiceTest.class,
    PaymentServiceTest.class
})
public class RegressionSuite {
}
```

Interview Tip:
A concise interview answer is:

"A test suite bundles several test classes so they run together as one unit. In JUnit 4 I'd annotate an empty class with @RunWith(Suite.class) and @Suite.SuiteClasses listing the test classes; in JUnit 5 the junit-platform-suite module provides @Suite with @SelectClasses instead."