Recipe to change assertTrue(a == null) to assertNull(a) and assertFalse(a == null) with assertNotNull

[yeikel]

This is similar to #200

Examples :

@Test
void myTest(){

String a = null;
String b =  "";
assertTrue(a == null);
assertFalse(a == null);

}

@Test
void myTest(){

String a = null;
String b = "";
assertNull(a);
assertNotNull(b);
}