How can we test if an array returns with different length?

Question

I want to test a method with signature int[] myMethod(int[] array, int removedElement) as argument. The method should remove the element if the element in in the array. As a result, the method may be able to return int[] with array.length - 1.

assertArrayEquals() does not confirm if the returned array has different length.

assertNotEquals() is not appropriate because the method may be removed wrongly more than one element.

How can I test this method?

Answer 1

Looking through the JUnit docs, I found assertEquals(long, long). You should be able to do something like this:

Assert.assertEquals("The array length is not what was expected!", (long) array.length - 1, (long) modifiedArray.length);

Assuming you're saving your modified array in the modifiedArray variable, of course.

(I have little to no experience with JUnit, so I could be totally wrong. If I am, let me know.)

Answer 2

There are two aspects to assert on:

• The length of the array
• The content of the array

It's true that the former will be implicitly tested with the latter, but I prefer to do that explicitly.

This makes it easy: store the length of the input and compare it with the output with assertEquals().

For the latter you take the input array (new[] { 5, 6 }) and output (new[] { 5 }) and you use assertArrayEquals() to compare the output with the result of your method, given the input and argument 6.