Examples of testing abstract class in Java

Dog.java

package virtualpet;

public class Dog extends VirtualPet {

	public Dog(String name) {
		super(name);
	}

	@Override
	public void tick() {
		// do tick stuff
	}

}

VirtualPet.java

package virtualpet;

public abstract class VirtualPet {

	private String name;

	public String getName() {
		return name;
	}

	public VirtualPet(String name) {
		this.name = name;
	}
	
	public abstract void tick();
}

VirtualPetTest.java

package virtualpet;

import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;

import org.junit.Test;

/**
 * Examples of different ways of creating the object under test when the class
 * is abstract, but we want to test the concrete bits of it.
 */
public class VirtualPetTest {

	@Test
	public void shouldAssignNameUsingAnonymousInnerClass() {
		VirtualPet underTest = createAnonymousTestInstance("Fido");

		/*
		 * same as assertEquals("Fido", underTest.getName()), but more expressive and
		 * less prone to error
		 */
		assertThat(underTest.getName(), is("Fido"));
	}

	private VirtualPet createAnonymousTestInstance(String name) {
		return new VirtualPet(name) {
			@Override
			public void tick() {
				// empty -- we're not testing this method
			}
		};
	}

	/**
	 * It can be very verbose to use anonymous inner classes, so sometimes a fake
	 * implementation is cleaner. Also, they may be easier to grasp for the
	 * unfamiliar.
	 */
	@Test
	public void shouldAssignNameUsingTestSubclass() {
		VirtualPet underTest = new TestVirtualPet("Fido");

		assertThat(underTest.getName(), is("Fido"));
	}

	private class TestVirtualPet extends VirtualPet {
		public TestVirtualPet(String name) {
			super(name);
		}

		@Override
		public void tick() {
			// empty -- we're not testing this method
		}
	}

	/**
	 * This may well be the best way -- create a concrete instance. This is not
	 * always possible (or desirable) in the wild, since there may be side effects
	 * or overhead or simply shite code.
	 */
	@Test
	public void shouldAssignNameUsingConcreteSubclass() {
		VirtualPet underTest = new Dog("Fido");

		assertThat(underTest.getName(), is("Fido"));
	}
}