Comparing arrays in JUnit assertions, concise built-in way?
Is there a concise, built-in way to do equals assertions on two like-typed arrays in JUnit? By default (at least in JUnit 4) it seems to do an instance compare on the array object itself.
EG, doesn't work:
int[] expectedResult = new int[] { 116800, 116800 };
int[] result = new GraphixMask().sortedAreas(rectangles);
assertEquals(expectedResult, result);
Of course, I can do it manually with:
assertEquals(expectedResult.length, result.length);
for (int i = 0; i < expectedResult.length; i++)
assertEquals("mismatch at " + i, expectedResult[i], result[i]);
..but is there a better way?
Use org.junit.Assert's method assertArrayEquals:
import org.junit.Assert;
...
Assert.assertArrayEquals( expectedResult, result );
If this method is not available, you may have accidentally imported the Assert class from junit.framework.
You can use Arrays.equals(..):
assertTrue(Arrays.equals(expectedResult, result));
I prefer to convert arrays to strings:
Assert.assertEquals(
Arrays.toString(values),
Arrays.toString(new int[] { 7, 8, 9, 3 }));
this way I can see clearly where wrong values are. This works effectively only for small sized arrays, but I rarely use arrays with more items than 7 in my unit tests.
This method works for primitive types and for other types when overload of toString returns all essential information.
assertEquals( Arrays.toString( new String[]{ "artiforg", "blobel", "kipple", "tench" } ), Arrays.toString( new String[]{ "artiforg", "blobel, kipple", "tench" } ) ); will pass. (The first array consists of three strings, the second of four strings.)
Assert.assertArrayEquals("message", expectedResult, result)
JUnit 5 we can just import Assertions and use Assertions.assertArrayEquals method
import org.junit.jupiter.api.Assertions;
Assertions.assertArrayEquals(resultArray,actualResult);
Using junit4 and Hamcrest you get a concise method of comparing arrays. It also gives details of where the error is in the failure trace.
import static org.junit.Assert.*
import static org.hamcrest.CoreMatchers.*;
//...
assertThat(result, is(new int[] {56, 100, 2000}));
Failure Trace output:
java.lang.AssertionError:
Expected: is [<56>, <100>, <2000>]
but: was [<55>, <100>, <2000>]
I know the question is for JUnit4, but if you happen to be stuck at JUnit3, you could create a short utility function like that:
private void assertArrayEquals(Object[] esperado, Object[] real) {
assertEquals(Arrays.asList(esperado), Arrays.asList(real));
}
In JUnit3, this is better than directly comparing the arrays, since it will detail exactly which elements are different.
Class Assertions in org.junit.jupiter.api
Use:
public static void assertArrayEquals(int[] expected,
int[] actual)
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java.lang.AssertionError: array lengths differed, expected.length=6 actual.length=7. As most JUnit failure messages it's not so helpful...I advise using some assertion frameworkAssert.assertFalse( Arrays.equals( expectedResult, result )).