Fuzzer generates values even when class is private

[Markoutte]

Description

Fuzzer creates values of private class. This leads to reflection-using by codegen, but fuzzer shouldn't create any tests using reflection.

To Reproduce

Try to generate code for test method:

public class AccessibleObjects {

    public boolean test(Inn.Node n) {
        return n.value * n.value == 36;
    }

    private static class Inn {
        static class Node {
            public int value;

            public Node() {

            }
        }
    }
}

Expected behavior

In this case fuzzer should not create any test, because Node object cannot be created by fuzzer (the Inn class is private).

Actual behavior

Fuzzer generates test with reflection that leads to another problem: #1629

    public void testTestReturnsFalse() throws ClassNotFoundException, NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchFieldException {
        AccessibleObjects accessibleObjects = new AccessibleObjects();
        Class nodeClazz = Class.forName("sanity.AccessibleObjects$Inn$Node");
        Constructor nodeConstructor = nodeClazz.getDeclaredConstructor();
        nodeConstructor.setAccessible(true);
        Object[] nodeConstructorArguments = new Object[0];
        Object node = nodeConstructor.newInstance(nodeConstructorArguments);
        Field valueField = nodeClazz.getDeclaredField("value");
        valueField.setAccessible(true);
        valueField.get(node) = 37;

        Class accessibleObjectsClazz = Class.forName("sanity.AccessibleObjects");
        Method testMethod = accessibleObjectsClazz.getDeclaredMethod("test", nodeClazz);
        testMethod.setAccessible(true);
        Object[] testMethodArguments = new Object[1];
        testMethodArguments[0] = node;
        boolean actual = ((Boolean) testMethod.invoke(accessibleObjects, testMethodArguments));

        assertFalse(actual);
    }

Environment

Fuzzing is set to 100%

Additional context

Looks like the problem is caused by different implementations of isAccessbile logic. We need to resolve #1507 to reduce errors like this.