spring-boot-tdd

This is based on the Test-Driven Development with Spring Boot talk given in SpringOne 2017

• Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle of Red, Green, Refactor

• Start a new "Web" Spring Boot project from Spring Boot Initialzr

Write MVC slice testing

Functionality to be tested

• The CarController, given a correct car name, i.e. "/cars/prius", should return success (200) and Car data in JSON format in the response body

• The CarController, given a non-existent car name, i.e. "/cars/nocar", should return failure (404)

• (Optional) The CarController, given a new car, should add it to the system and return success (201) with response body containing newly added car

Tips

• Use @WebMvcTest, which automatically configures MockMvc object

• Given that it is a unit testing, you should mock CarService object - think about which one to use, @Mock or @MockBean

• In Spring, all exceptions should be RunTimeException

• Observe how much time this test takes and see if Tomcat gets started or not

Write Service slice testing

Functionality to be tested

• The CarService's getCarDetails method, given a correct car name, "prius", should return Car object

• The method, given a non-existent car name, "nocar", should throw CarNotFoundException

• (Optional) The CarService's addCar(Car car) method should add it to the system and return added Car

Tips

• Since this is a unit testing, you should mock CarRepository object

• Start with testing with Spring using @RunWith(SpringRunner.class) (using Spring testing framework) and then refactor it with @RunWith(MockitoJUnitRunner.class) and think about which one is a better practice

Trouble-shooting

• If you experience the following error, it is because you have not handle the case where CarRepository's findByName(..) method returns null.

  java.lang.AssertionError: Expected exception: com.example.demotdd5.CarNotFoundException
  
  ...
  org.h2.jdbc.JdbcSQLException: Database is already closed (to disable automatic closing at VM shutdown, add ";DB_CLOSE_ON_EXIT=FALSE" to the db URL) [90121-197]
  at org.h2.message.DbException.getJdbcSQLException(DbException.java:357)
  at org.h2.message.DbException.get(DbException.java:179)
  at org.h2.message.DbException.get(DbException.java:155)
  

Write JPA Repository slice testing

Functionality to be tested

• The CarRepository's findByName(..) method should return a Car given a valid car name

• (Optional) The CarRepository's save(..) method should return a Car give a Car object

Tips

• Use @DataJpaTest annotation, which provides TestEntityManager

Trouble-shooting

• When your test fails below fails with org.springframework.orm.jpa.JpaSystemException: No default constructor for entity: .., it means your Car class does not have a default constructor

      @Test
      public void findByName_should_return_car_given_valid_car() 
                throws Exception {
  
      // arrange
      testEntityManager.persistAndFlush(new Car("camry", "regular"));
      testEntityManager.clear();
  
      // act and assert
      Car car = carRepository.findByName("camry");
      assertThat(car).isEqualTo(new Car("camry", "regular"));
  
      // verify
  }
  

Write Service caching slice testing

Functionality to be tested

• The CarService's getCarDetails(..) method should return an item from a cache if it gets called more than once

Tips

• The way you can test the caching behavior is to call CarService's getCarDetails(..) method twice and then see if it called CarRepository's findByName(..) method once

Write integration testing

Functionality to be tested

• The application, when accessed with "/cars/prius", should return success (200)

  • Assert that return status is 200
  • Assert that content type returned MediaType.APPLICATION_JSON_UTF8
  • Assert that the body returns Car, name and type of which are "prius" and "hybrid" respectively

Tips

• Use @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
• Observe how much this test takes, also observe that this test starts Tomcat