@Test
public void mockUnitTest() {

	MessageService messageService = mock(MessageService.class);
	// when(messageService.generateMessage("Luke")).thenReturn("Foo!");
	when(messageService.generateMessage(anyString())).thenReturn("Foo!");
	GreetingClient client = new GreetingClient(messageService);
	assertEquals("FOO!", client.greetUser("doesn't matter"));
	// Optionally verify how mock was used.
	// verify(messageService).generateMessage("doesn't matter");
}