Getting started with junit-quickcheck

  • Create a class to host the properties you want to verify about a part of your system. Mark it with the annotation @RunWith(JUnitQuickcheck.class).
  • Add public methods with a return type of void on your class, to represent the individual properties. Mark each of them with the annotation @Property.
  • Run your class using JUnit. Each of your properties will be verified against several randomly generated values for each of the parameters on the properties’ methods.
    import com.pholser.junit.quickcheck.runner.JUnitQuickcheck;
    import com.pholser.junit.quickcheck.Property;

    class Crypto {
        byte[] encrypt(byte[] plaintext, Key key) {
            // ...

        byte[] decrypt(byte[] ciphertext, Key key) {
            // ...

    public class SymmetricKeyCryptographyProperties {
        @Property public void decryptReversesEncrypt(String plaintext, Key key)
            throws Exception {

            Crypto crypto = new Crypto();

            byte[] ciphertext =
                crypto.encrypt(plaintext.getBytes("US-ASCII"), key);

                new String(crypto.decrypt(ciphertext, key)));

Note: The example above presumes the existence and availability of generators for classes String and Key. Find out more about generators in Basic Types and Generating Values of Other Types.

junit-quickcheck honors the usual JUnit machinery: @Before, @After, @Rule, @BeforeClass, @AfterClass, @ClassRule. It will also run zero-arg public void methods annotated with @Test.