Example of a base class for models.

ModelTestBase.java

/**
 * The base class for models.
 *
 * @param <T> The type of the model under test.
 */
public abstract class ModelTestBase<T extends Serializable> {

  /**
   * Responsible for generating a test instance.
   *
   * @return A test instance; never {@code null}
   */
  public abstract T newTestInstance();

  /**
   * Responsible for generating a second test instance which is equivalent to the given instance,
   * but is not the same instance.
   *
   * @param base The base unit; never {@code null}.
   * @return An instance, {@code it}, which is not the same as {@code base}, but where {@code base.equals(it)} will return {@code true}
   */
  public T newEquivalentTestInstance(T base) {
    // Don't worry about optimizing this: it's test code.
    try {
      final ByteArrayOutputStream baos = new ByteArrayOutputStream();
      final ObjectOutputStream oos = new ObjectOutputStream(baos);
      oos.writeObject(base);
      final ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
      final ObjectInputStream ois = new ObjectInputStream(bais);
      return getClassUnderTest().cast(ois.readObject());
    } catch(Exception e) {
      throw new RuntimeException("Error cloning test instance", e);
    }
  }

  public Class<T> getClassUnderTest() {
    return (Class<T>)newTestInstance().getClass();
  }

  /**
   * Basic sanity check to make sure that we aren't generating null test instances.
   */
  @Test
  public void testNewTestInstanceIsNotNull() {
    assertNotNull(newTestInstance());
  }

  /**
   * Basic sanity check to make sure that we aren't generating null values for the class under test.
   */
  @Test
  public void testClassUnderTestIsNotNull() {
    assertNotNull(getClassUnderTest());
  }

  @Test
  public void testNewEquivalentTestInstanceDoesNotReturnSame() {
    T testInstance = newTestInstance();
    assertEquals(testInstance, newEquivalentTestInstance(testInstance));
    assertNotSame(testInstance, newEquivalentTestInstance(testInstance));

    // Don't be cute.
    assertNotSame(newEquivalentTestInstance(testInstance), newEquivalentTestInstance(testInstance));
  }

  @Test
  public void testNewTestInstanceIsNotEqualToAnotherNewTestInstance() {
    T left = newTestInstance();
    T right = newTestInstance();
    assertNotSame(left, right);
    assertNotEquals(left, right);
  }

  @Test
  public void testHasSerializableUUIDField() throws Exception {
    Field field = getClassUnderTest().getField("UUID");
    assertNotNull(field);
    assertTrue(Modifier.isFinal(field.getModifiers()));
    assertTrue(Modifier.isStatic(field.getModifiers()));
    // Add any other checks here (not 0?)
  }

  @Test
  public void testHashCode() {
    T it = newTestInstance();
    T equals = newEquivalentTestInstance(left);
    T notEquals = newTestInstance();
    assertEquals(it.hashCode(), equals.hashCode());
    assertNotEquals(it.hashCode(), notEquals.hashCode());
  }

  @Test
  public void testEquals() {
    T it = newTestInstance();
    T equals = newEquivalentTestInstance(left);
    T notEquals = newTestInstance();
    assertEquals(it, equals);
    assertNotEquals(it, notEquals);
  }



}