@Test
public void createUserTest() {

    //Setup:
    FormDataMultiPart fd = new FormDataMultiPart();
    fd.field("username", "testUser");
    fd.field("email", "example@example.com");
    fd.field("firstName", "John");
    fd.field("lastName", "Doe");
    fd.field("password", "123");
    fd.field("roles", "admin");
    fd.field("roles", "user");
    when(engineManager.userExists(anyString())).thenReturn(false);
    Response response = target().path("users")
            .request().post(Entity.entity(fd, MediaType.MULTIPART_FORM_DATA));
    assertEquals(response.getStatus(), 201);
    verify(engineManager).storeUser(eq(ENGINE_NAME), any(User.class));
}