Used to assert that Associative array is empty.
The expected associative array.
The file name that the assert failed in. Should be left as default.
The file line that the assert failed in. Should be left as default.
If the Associative array is not empty, will throw an UnitTestException with expected and actual values.
// Will throw an exception like "UnitTestException@example.d(6): Expected empty Associative Array, but got <["test":12]>" ["test":12].shouldBeEmpty();