How to dynamically load different class for JUnit tests? - spring

Question

I've written a couple of JUnit tests to test my REST functionality. Since I only want to test REST (and not the database, domain logic, ..) I made a stub filles with dummy data which stands for the rest of the backend.
[EDIT] For example I want to test /customers/all
A GET request will be responded to with an arraylist containing all names.
I therefore use MockMV.
this.mockMvc.perform(get("/customers/all").accept("application/json"))
.andExpect(status().isOk())
.andExpect(jsonPath("$").isNotEmpty())
.andExpect(jsonPath("$[0].name", is("John")));
When you normally perform a GET request towards /customers/all a request will be sent to the database. Now, to test my REST controller I made a stub which responds to GET /customers/all with a simple arraylist containing just my name (as you can see in the test). When I test this local I simply replace the real class with this stub. How is this done dynamically?

Answer 1

I don't think your approach is the good one. Just use your real controller, but stub its dependencies (using Mockito, for example), just like you would do for a traditional unit test.
Once you have an instance of the controller using stubbed dependencies, you can use a standalone setup and use MockMvc to test, in addition to the controller code, the mapping annotations, the JSON marshalling, etc.
Thias approach is described in the documentation.
Example using Mockito, assuming the controller delegates to a CustomerService:
public class CustomerControllerTest {
#Mock
private CustomerService mockCustomerService;
#InjectMocks
private CustomerController controller;
private MockMvc mockMvc;
#Before
public void setup() {
MockitoAnnotations.initMocks(this);
this.mockMvc = MockMvcBuilders.standaloneSetup(controller).build();
}
#Test
public void shouldListCustomers() {
when(mockCustomerService.list()).thenReturn(
Arrays.asList(new Customer("John"),
new Customer("Alice")));
this.mockMvc.perform(get("/customers").accept("application/json"))
.andExpect(status().isOk())
.andExpect(jsonPath("$").isNotEmpty())
.andExpect(jsonPath("$[0].name", is("John")));
}
}