Unit Testing
Mockito spy vs. mock There is couple important difference between the two. 1. With spy , if you are not careful , you may end up calling the real code , while your intention is to mock it. Mockito.when(spy.methodToMock()).thenReturn(true); This will end up calling the real method on spy. if you want , not to call the real code, use different syntax. Mockito.doReturn(true).when(spy).methodToMock(); 2. Usage of assertThat([value], [matcher statement]); assertThat(x, is(3)); assertThat(x, is(not(4))); assertThat(responseString, either(containsString("color")).or(containsString("colour"))); assertThat(myList, hasItem("3")); Useful Links: https://www.springboottutorial.com/unit-testing-for-spring-boot-rest-services