How to check returntype in Spring Unittest using MockMVC? - spring

Question

The Spring method I wanna test
#RequestMapping(value="/files", method=RequestMethod.GET)
#ResponseBody
public List<FileListRequest> get() {
return getMainController().getAllFiles();
}
I want to be assured all calls to /files are responded with an List[FileListRequest]. How?
This is the method in which the test is supposed to be.
#Test
public void testGetAll() throws Exception {
this.mockMvc.perform(get("/files").accept("application/json"))
.andExpect(status().isOk())
.andExpect(content().contentType(SOMETHING);
}
Can I simply replace the SOMETHING or am I totally wrong?
Can I run assert methods on the object returned by perform()?

Answer 1

Edit:
MvcResult result = this.mockMvc.perform(get("/files").accept("application/json"))
.andExpect(status().isOk())
.andReturn();
String content = result.getResponse().getContentAsString();
// Convert json String to Respective object by using Gson or Jackson
ObjectMapper mapper = new ObjectMapper();
TypeFactory typeFactory=objectMapper.getTypeFactory();
List<SomeClass> someClassList =mapper.readValue(content , typeFactory.constructCollectionType(List.class, SomeClass.class));
//Assert here with your list
You could use Json Path to check if specific data exist in your response
a code snipper from by old project
mockMvc.perform(get("/rest/blogs")) .contentType(MediaType.APPLICATION_JSON))
.andExpect(jsonPath("$.blogs[*].title",
hasItems(endsWith("Title A"), endsWith("Title B"))))
.andExpect(status().isOk());

Answer 2

You cannot use contentType to check the class of instances. The Content-Type is to determine the format of text sent/returned in a HTTP(S) request/response, and has nothing to do with programmatic type-check. It only regulates that the request/response is in json/text-plain/xml, etc.
To check the type of the objects returned in the response, let's assume that the response is in format JSON(built-in Jackson in Spring boot will do the (un)marshalling), and we just use org.hamcrest.Matchers.instanceOf(Class<?> type) to check the class of first item in the list, with jsonPath.
A working snippet:
import static org.hamcrest.Matchers.instanceOf;
...
#Test
public void testBinInfoControllerInsertBIN() throws Exception {
when(this.repository.save(mockBinInfo)).thenReturn(mockBinInfo);
this.mockMvc.perform(post("/insert")
.content("{\"id\":\"42\", \"bin\":\"touhou\", \"json_full\":\"{is_json:true}\", \"createAt\":\"18/08/2018\"}")
.accept(MediaType.APPLICATION_JSON_UTF8_VALUE)
.contentType(MediaType.APPLICATION_JSON_UTF8_VALUE)
)
.andExpect(content().contentType(MediaType.APPLICATION_JSON_UTF8_VALUE))
.andExpect(status().isCreated())
.andExpect(jsonPath("$[0]", instanceOf(BinInfo.class)))
.andExpect(jsonPath("$[0].bin", is("touhou")));
}
If you want to check every item in the list... maybe it is redundant? I haven't seen code examining each and every item in the list because you have to iterate. There is way, of course.