Assertions on nullable object fields in parametrized tests

[EgorkaKulikov]

Description

Parametrized tests fails with NullPointerException due to incorrect assertions in them

To Reproduce

1. Create parametrized tests with JUnit5 on CastExample.simpleCast from utbot-samples
2. The generated code uses deepEquals to assert result object field states, but this object is null in one of the cases

@ParameterizedTest
@MethodSource("provideDataForSimpleCast")
public void parameterizedTestsForSimpleCast(CastExample castExample,
                                            CastClass castClass,
                                            CastClassFirstSucc expectedResult,
                                            Class<Throwable> expectedError
) {
    try {
        CastClassFirstSucc actual = castExample.simpleCast(castClass);
        int expectedResultZ = expectedResult.z;
        int actualZ = actual.z;
        assertEquals(expectedResultZ, actualZ);

        int expectedResultX = expectedResult.x;
        int actualX = actual.x;
        assertEquals(expectedResultX, actualX);

        int expectedResultDefaultValue = expectedResult.defaultValue;
        int actualDefaultValue = actual.defaultValue;
        assertEquals(expectedResultDefaultValue, actualDefaultValue);
    } catch (Throwable throwable) {
        assertTrue(expectedError.isInstance(throwable));
    }
}

Actual behavior

This test fails with NPE on the following set of arguments

{
    CastExample castExample = new CastExample();
    argList.add(Arguments.arguments(castExample, null, null, null));
}

The exception is

java.lang.NullPointerException
	at algorithms.casts.CastExampleTest.parameterizedTestsForSimpleCast(CastExampleTest.java:39)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)

[EgorkaKulikov]

The solution for the majority of cases is

try {
    CastClassFirstSucc actual = castExample.simpleCast(castClass);

    if (expectedResult == null) {
        assertNull(actual);
    } else {
        int expectedResultZ = expectedResult.z;
        int actualZ = actual.z;
        assertEquals(expectedResultZ, actualZ);

        int expectedResultX = expectedResult.x;
        int actualX = actual.x;
        assertEquals(expectedResultX, actualX);

        int expectedResultDefaultValue = expectedResult.defaultValue;
        int actualDefaultValue = actual.defaultValue;
        assertEquals(expectedResultDefaultValue, actualDefaultValue);
    }
}

Bit it will not fix the problem of nulls not only on the top layer.
Possibly we need to introduce special deepEquals method for parametrized tests.