Use controllers via MockMvc in Spring integration tests

[IlyaMuravjov]

Description

Fixes #2345
Also fixes #2227

This PR makes integration tests for Spring controllers instead of calling controllers directly, call them via MockMvc.perform() and use andExpect() to do asserts.

In order to achieve that:

• methodUnderTest and methodToCall were separated (methodToCall can be set in EnvironmentModels)
• ConcreteExecutionContext was allowed to modify stateBefore (including methodToCall)
• UtCustomModel was introduced to describe models with additional custom data (it has origin that can be used in common UtBot code base)
• InstrumentationContext was enriched to provide UtCustomModelConstructors (including previously existing subclasses of UtAssembleModelConstructorBase)
• CgSimpleCustomAssertConstructor was introduced to generate more human readable assertions when expectedResult is UtCustomModel (makes Avoid generating many reflection statements for LinkedHashMap #2227 no longer relevant for Spring controllers)

Example:

@SpringBootTest
@BootstrapWith(SpringBootTestContextBootstrapper.class)
@DirtiesContext(classMode = DirtiesContext.ClassMode.BEFORE_EACH_TEST_METHOD)
@Transactional
@AutoConfigureTestDatabase
@AutoConfigureMockMvc
public final class OrderControllerTest {
    @Autowired
    private MockMvc mockMvc;

    @Autowired
    private OrderRepository orderRepository;

    @Autowired
    private ObjectMapper jacksonObjectMapper;

    @Test
    @DisplayName("saveOrder: order = Order()")
    public void testSaveOrder1() throws Exception {
        Object[] objectArray = {};
        MockHttpServletRequestBuilder mockHttpServletRequestBuilder = post("/api/orders", objectArray);
        MediaType mediaType = valueOf("application/json");
        MockHttpServletRequestBuilder mockHttpServletRequestBuilder1 = mockHttpServletRequestBuilder.contentType(mediaType);
        Order order = new Order();
        String string = jacksonObjectMapper.writeValueAsString(order);
        MockHttpServletRequestBuilder mockHttpServletRequestBuilder2 = mockHttpServletRequestBuilder1.content(string);

        ResultActions actual = mockMvc.perform(mockHttpServletRequestBuilder2);

        actual.andDo(print());
        actual.andExpect((status()).is(201));
        actual.andExpect((content()).string("{\"id\":28,\"buyer\":null,\"price\":null,\"qty\":0}"));
    }
}

How to test

Manual tests

Generate integration tests for OrderController in spring-boot-testing project, there should be tests that use MockMvc.

Self-check list

• I've set the proper labels for my PR (at least, for category and component).
• PR title and description are clear and intelligible.
• I've added enough comments to my code, particularly in hard-to-understand areas.
• The functionality I've repaired, changed or added is covered with automated tests.
• Manual tests have been provided optionally.
• The documentation for the functionality I've been working on is up-to-date.