Rest-assured. How to check if not empty array is returned?

Question

I have the following code which should test my RESTful API:

given().baseUri("http://...").get("/categories/all")
    .then()
    .body(
        "results",  not(empty())
    );

The API returns the following response:

{
    "error": {
        "type": "NotFoundException"
    }
}

And I want the test to fail for such response. But the test passes.

How can I modify the test to make it fail? It should only pass if the API returns an object which contains a not-empty array in the "results" key. It should fail when the "results" key does not exists, contains empty array or when it contains something that is not an array.

Answer 1

I came up with the following solution:

given().baseUri("http://...").get("/categories/all")
    .then()
    .body(
        "results", hasSize(greaterThan(0))
    );

It fails if "results" is an empty array or not an array. It passes if "results" is a not-empty array. It reports an error in a readable way, e.g.:

Expected: a collection with size a value greater than <0>
Actual: null