Introduce fuzzing in Spring unit tests

[IlyaMuravjov]

Description

Fixes #2321

To be compatible with Spring unit test paradigm fuzzer is made to mock all third party classes (other than class under test and some well know types, e.g. primitives, lists, and so on) and construct UtCompositeModel for class under test, so mocks can be injected into it with @InjectMock.

Example of fuzzer generated test (ownerRepositoryMock is injected into ownerController via @InjectMocks):

@Test
public void testProcessFindFormByFuzzer() {
	Page pageMock1 = mock(Page.class);
	(when(pageMock1.isEmpty())).thenReturn(false);
	(when(pageMock1.getTotalElements())).thenReturn(0L, 0L);
	List listMock1 = mock(List.class);
	(when(pageMock1.getContent())).thenReturn(listMock1);
	(when(pageMock1.getTotalPages())).thenReturn(0);
	(when(ownerRepositoryMock.findByLastName(any(), any()))).thenReturn(pageMock1);
	Owner ownerMock = mock(Owner.class);
	(when(ownerMock.getLastName())).thenReturn(((String) null), ((String) null));
	((doNothing()).when(ownerMock)).setLastName(any());
	BindingResult resultMock = mock(BindingResult.class);
	Model modelMock = mock(Model.class);
	Model modelMock1 = mock(Model.class);
	(when(modelMock.addAttribute(any(), any()))).thenReturn(modelMock1, modelMock1, modelMock1, modelMock1, modelMock1);

	String actual = ownerController.processFindForm(1073741824, ownerMock, resultMock, modelMock);

	String expected = "owners/ownersList";

	assertEquals(expected, actual);
}

How to test

Manual tests

Generate unit tests with fuzzing ratio set to 100% for OwnerController.

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.
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• 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.