Show path to first mismatch on failure

[davidje13]

I'm on a project where we're using JSON matching for our integration tests to check actual results against fixture files. We use the matchers with RestAssured like this:

RestAssured.when().post('url')
    .then().body(jsonEquals(myContentLoadedFromAFixture).when(IGNORING_EXTRA_FIELDS));

It works great for checking success/failure, but the debug message when failing is, frustratingly, just a copy of the entire expected vs actual JSON content, for example:

java.lang.AssertionError: 1 expectation failed.
Response body doesn't match expectation.
Expected: {
"foo": "bar",
"zig": "zag"
}

Actual: {"zig": "zag", "foo": "baz"}

Which is problematic when working with large JSON bodies.

It looks like #44 would be a full solution to this problem, but has issues of its own (how to skip past ignored fields, for example).

A simpler fix would save us a huge amount of time: as well as providing the mismatched content, also give the path to the first failure. Something like:

java.lang.AssertionError: 1 expectation failed.
Response body doesn't match expectation.
Expected: {
"foo": "bar",
"zig": "zag"
}

Actual: {"zig": "zag", "foo": "baz"}
First mismatch: $.foo

[davidje13]

I did some more investigation and found that RestAssured uses its own match failure messages by default (which is where the output above is coming from). So I guess this isn't an issue to raise here.