Confusing error message when the length of two multidimensional arrays are not equal

[mattj256]

Current behavior:

assertArrayEquals((new Object[1][3]), (new Object[1][4]));
// throws ArrayComparisonFailure with message:
// "array lengths differed, expected.length=3 actual.length=4"

If I got this message I would assume that the FIRST dimension was different, but in this example it's the second dimension that's different. Is anyone bothered by this?

[devslash-paul]

This is expected behaviour for a JUnit test. The first is the expected and the second argument is the comparison. Therefore in this case the expected.length = 3 and actual.length = 4 when the inner array in the 2D array is being checked for length

[kcooney]

Can anyone on this thread suggest a better error message?

[Stephan202]

If the two arrays at depth N have different lengths, then that's just another instance of two elements at depth N - 1 being unequal. We already have code to construct a nice error message for this situation, in the form of the ArrayComparisonFailure class.

Thus, I claim the error message for the given example should simply be this:

arrays first differed at element [0]; array lengths differed, expected.length=3 actual.length=4

If you agree, I can open a PR with this small fix:

$ git diff --stat
 src/main/java/org/junit/internal/ComparisonCriteria.java   | 11 +++++++++--
 src/test/java/org/junit/tests/assertion/AssertionTest.java | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

[kcooney]

@Stephan202 sounds reasonable. Please make the pull request against the junit5 branch

[Stephan202]

@kcooney: Cool, I opened #1054.