Junit test case AssertionError expected to be a json string

Question

I'm trying to create a helper method to transform the response body of a MockMvc test back into my domain objects and want to make it generic for all objects. It works when the response is an object but not when it's a list of objects.

I'm using com.fasterxml.jackson.databind.ObjectMapper and com.fasterxml.jackson.core.type.TypeReference to map the response body back into my application objects.

These are the methods that map the responses to objects:

  protected static <T> List<T> getResponseBodyList(MockHttpServletResponse response,
      Class<T> clazz) throws JsonParseException, JsonMappingException,
      UnsupportedEncodingException, IOException, InstantiationException, IllegalAccessException {
    TypeReferenceListImpl<T> typeReference = new TypeReferenceListImpl<T>(clazz);
    List<T> responseBody = new ObjectMapper().readValue(response.getContentAsString(),
        typeReference);
    return (List<T>) responseBody;
  }

  protected static <T> T getResponseBody(MockHttpServletResponse response, Class<T> clazz)
      throws JsonParseException, JsonMappingException, UnsupportedEncodingException, IOException {
    TypeReferenceImpl<T> typeReference = new TypeReferenceImpl<T>(clazz);
    T responseBody = new ObjectMapper().readValue(response.getContentAsString(), typeReference);
    return responseBody;
  }

  private static class TypeReferenceImpl<T> extends TypeReference<T> {
    protected final Type type;

    protected TypeReferenceImpl(Class<T> clazz) {
      type = clazz;
    }

    public Type getType() {
      return type;
    }
  }

  private static class TypeReferenceListImpl<T> extends TypeReference<T> {
    protected final Type type;

    protected TypeReferenceListImpl(Class<T> clazz) throws InstantiationException,
        IllegalAccessException {
      List<T> list = new ArrayList<>();
      list.add(clazz.newInstance());
      type = list.getClass();
    }

    public Type getType() {
      return type;
    }
  }

I'm calling these methods like this in my tests:

// This test works: 
  @Test
  public void getUserTest() throws Exception {
    when(applicationUserServiceMock.loadUserByUsername(applicationUser.getUsername())).thenReturn(
        applicationUser);

    MockHttpServletResponse response = executeGet(API_V1_ADMIN_APPLICATION_USERS + applicationUser
        .getUsername());
    ApplicationUser responseBody = getResponseBody(response, ApplicationUser.class);

    verifyResponseStatus(response, HttpStatus.OK.value());
    assertEquals(applicationUser, responseBody);
  }

//Test that fails:
 @Test
  public void getUsersTest() throws Exception {
    when(applicationUserServiceMock.getAllUsers()).thenReturn(applicationUsersList);

    MockHttpServletResponse response = executeGet(API_V1_ADMIN_APPLICATION_USERS); 

    List<ApplicationUser> responseBody = getResponseBodyList(response, ApplicationUser.class);

    verifyResponseStatus(response, HttpStatus.OK.value());
    assertEquals(3, responseBody.size()); // This assert passes
    assertEquals(applicationUsersList, responseBody); 
// Fails in the last assertEquals. Debugging it, I can see responseBody ends up being a List of LinkedHashMaps. 
// I assume because I get a list of Objects instead of a list of ApplicationUsers. 
  }

What I need for this to work (at least as a first approach), is to get TypeReferenceListImpl to return the type of list of the real class of T, which I'm passing as a parameter Class clazz. But I can't seem to create a list of that specific type based on a Class object to get it's type with getClass(). This is the last of many approaches I took to get that type, but none worked.

Is it even possible? Or does someone have another approach to solve this problem?

I'm trying to make a generic method to get the response body for all controller tests that return different types of lists of objects

The stack trace is:

java.lang.AssertionError: expected:<[{
  "id" : 1001,
  "username" : "goku",
  "password" : null,
  "email" : "goku@dbz.com",
  "firstName" : "Goku",
  "lastName" : "Son",
  "lastLogin" : null,
  "authorities" : [ {
    "id" : 10,
    "name" : "ADMIN_ROLE"
  } ],
  "accountNonExpired" : true,
  "accountNonLocked" : true,
  "credentialsNonExpired" : true,
  "enabled" : true
}, {
  "id" : 1002,
  "username" : "gohan",
  "password" : null,
  "email" : "gohan@dbz.com",
  "firstName" : null,
  "lastName" : null,
  "lastLogin" : null,
  "authorities" : [ {
    "id" : null,
    "name" : "ROLE_USER"
  } ],
  "accountNonExpired" : true,
  "accountNonLocked" : true,
  "credentialsNonExpired" : true,
  "enabled" : true
}, {
  "id" : 1003,
  "username" : "goten",
  "password" : null,
  "email" : "goten@dbz.com",
  "firstName" : null,
  "lastName" : null,
  "lastLogin" : null,
  "authorities" : [ {
    "id" : null,
    "name" : "ROLE_USER"
  } ],
  "accountNonExpired" : true,
  "accountNonLocked" : true,
  "credentialsNonExpired" : true,
  "enabled" : true
}]> but was:<[{id=1001, username=goku, password=null, email=goku@dbz.com, firstName=Goku, lastName=Son, lastLogin=null, authorities=[{id=10, name=ADMIN_ROLE}], accountNonExpired=true, accountNonLocked=true, credentialsNonExpired=true, enabled=true}, {id=1002, username=gohan, password=null, email=gohan@dbz.com, firstName=null, lastName=null, lastLogin=null, authorities=[{id=null, name=ROLE_USER}], accountNonExpired=true, accountNonLocked=true, credentialsNonExpired=true, enabled=true}, {id=1003, username=goten, password=null, email=goten@dbz.com, firstName=null, lastName=null, lastLogin=null, authorities=[{id=null, name=ROLE_USER}], accountNonExpired=true, accountNonLocked=true, credentialsNonExpired=true, enabled=true}]>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:118)
    at org.junit.Assert.assertEquals(Assert.java:144)
    at com.nicobrest.kamehouse.admin.controller.ApplicationUserControllerTest.getUsersTest(ApplicationUserControllerTest.java:91)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:239)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
...

Update: In case someone runs into this, you don't need to manually create the list, jackson mapper already has a built in way to crate a list of a generic type you pass (facepalm), so my final solution is using these 2 methods:

  protected static <T> List<T> getResponseBodyList(MockHttpServletResponse response, Class<T> clazz)
      throws JsonParseException, JsonMappingException, UnsupportedEncodingException, IOException,
      InstantiationException, IllegalAccessException {
    ObjectMapper mapper = new ObjectMapper();
    List<T> responseBody = mapper.readValue(response.getContentAsString(),
        mapper.getTypeFactory().constructCollectionType(List.class, clazz));
    return responseBody;
  }

  protected static <T> T getResponseBody(MockHttpServletResponse response, Class<T> clazz)
      throws JsonParseException, JsonMappingException, UnsupportedEncodingException, IOException {
    ObjectMapper mapper = new ObjectMapper();
    T responseBody = mapper.readValue(response.getContentAsString(),
        mapper.getTypeFactory().constructType(clazz));
    return responseBody;
  }

Thanks @deadpool for your sugesstions and making me look at it from a different point of view

Answer 1

The problem is applicationUsersList is a json string or List<JsonObject> and responseBody is List<ApplicationUser> were both are not equal. either convert applicationUsersList to List<ApplicationUser> using ObjectMapper

public <T> T readValue(String src,
          TypeReference valueTypeRef)
        throws IOException,
               JsonParseException,
               JsonMappingException

Or you can convert List<ApplicationUser> to json string or List<JsonObject>

public String writeValueAsString(Object value)
                      throws JsonProcessingException