CODEWITHSUNDEEP
javaunit-testingjunit
Photon Point
Photon Point

Reputation: 808

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

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?

Upvotes: 3

Views: 8863

Answers (3)

Adam
Adam

Reputation: 36733

I'd still test using arrayAssertsEquals, just craft your inputs and expected results using new int[]{}

@Test
public void shrinksArray() {
    assertArrayEquals(new int[] { 2, 3 }, remove(new int[] { 1, 2, 3 }, 1));
    assertArrayEquals(new int[] { 1, 2 }, remove(new int[] { 1, 2, 3 }, 3));
    assertArrayEquals(new int[] { 1, 3 }, remove(new int[] { 1, 2, 3 }, 2));
    assertArrayEquals(new int[] { 1, 2, 3 }, remove(new int[] { 1, 2, 3 }, 9));
}

Or if you're crazy about single assertions per test...

private static final int[] ORIGINAL = new int[] { 1, 2, 3 };

@Test
public void removesFromBeginning() {
    assertArrayEquals(new int[] { 2, 3 }, remove(ORIGINAL, 1));
}

@Test
public void removesFromEnd() {
    assertArrayEquals(new int[] { 1, 2 }, remove(ORIGINAL, 3));
}

@Test
public void removesFromMiddle() {
    assertArrayEquals(new int[] { 1, 3 }, remove(ORIGINAL, 2));
}

@Test
public void doesNotRemoveUnknownItem() {
    assertArrayEquals(ORIGINAL, remove(ORIGINAL, 9));
}

Upvotes: 2

anon
anon

Reputation:

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.)

Upvotes: 3

Jeroen Vannevel
Jeroen Vannevel

Reputation: 44448

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.

Upvotes: 2

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