How do I Dynamically create a Test Suite in JUnit 4?

To create a dynamic test suite, you need to use the @RunWith annotation. There are two common ways to use it:

@RunWith(Suite.class)

This allows you to specify, which classes compose the test suite in question. This is equivalent to the JUnit 3 style:

import junit.framework.TestSuite;
import junit.framework.TestCase;

public final class MasterTester extends TestCase {

  public static TestSuite suite() {
    TestSuite suite = new TestSuite();
    suite.addTestSuite(TestClass1.class);        
    suite.addTestSuite(TestClass2.class);
    // etc...
    return suite;
  }
}

The equivalent JUnit 4 class will be:

import org.junit.runners.Suite;

@RunWith(Suite.class)
@SuiteClasses({TestClass1.class, TestClass2.class})
public final class MasterTester {

}

@RunWith(AllTests.class)

This allows you to dynamically specify the tests, which compose the test suite. If your tests are not known until runtime, you cannot specify them in the annotations. You can use this construction instead. So, if the JUnit 3 code is:

import junit.framework.TestCase;
import junit.framework.TestSuite;
import junit.framework.Test;

public final class MasterTester extends TestCase {

  public static TestSuite suite() {
    TestSuite suite = new TestSuite();
    for (Test test : findAllTestCasesRuntime()) {
      suite.addTest(test);
    }
    return suite;
  }
}

The equivalent JUnit 4 code will be:

import org.junit.runners.AllTests;
import junit.framework.TestSuite;
import junit.framework.Test;

@RunWith(AllTests.class)
public final class MasterTester {

  public static TestSuite suite() {
    TestSuite suite = new TestSuite();
    for (Test test : findAllTestCasesRuntime()) {
      suite.addTest(test);
    }
    return suite;
  }
}