Can assertEquals(Long,Integer) succeed?

Question

Currently I am doing some code review and I found this line of code which interrupts the testcase:

assertEquals(Long.valueOf(4321), lMessage.getNumber());

getNumber returns an Integer which is also 4321. I changed it to this:

assertTrue(4321 == lSavedStoerung.getMessage());

because in my understanding of the equals method the assertEquals can never return true in the first example. With my assertTrue all test cases running fine.

Or did I understand something wrong?

Answer 1

The reason why assertEquals test has failed is that equality considers not only the value of the number, but also its type. java.lang.Long object does not compare as equal to a java.lang.Integer.

Since lMessage.getNumber() returns an int, Java wraps it into Integer before passing to assertEquals. That's why you could fix the test case by using Integer.valueOf instead:

assertEquals(Integer.valueOf(4321), lMessage.getNumber());

Answer 2

What is the reason behind 4321 being a long? If it's not necessary use the integer solution dasblinkenlight sugested.

assertEquals(Integer.valueOf(4321), lMessage.getNumber());

or

assertEquals(4321, lMessage.getNumber());

On the other hand, if your code allows lMessage.getNumber() return a long depending on the circumstances then you could box it into a long for your test.

assertEquals(Long.valueOf(4321), (long) lMessage.getNumber());

PS: Getting too compfortable using assertTrue & == will cause you trouble if you ever compare something that does not come in a primitive data type, but it will not in this specific example.