Function assert_approx_equals

test/fixtures/wpt/resources/testharness.js:1799–1819

* Assert that ``actual`` is within ± ``epsilon`` of ``expected``. * * @param {number} actual - Test value. * @param {number} expected - Value number is expected to be close to. * @param {number} epsilon - Magnitude of allowed difference between ``actual`` and ``expected``. *

(actual, expected, epsilon, description)

     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_approx_equals(actual, expected, epsilon, description)
    {
        /*
         * Test if two primitive numbers are equal within +/- epsilon
         */
        assert(typeof actual === "number",
               "assert_approx_equals", description,
               "expected a number but got a ${type_actual}",
               {type_actual:typeof actual});

        // The epsilon math below does not place nice with NaN and Infinity
        // But in this case Infinity = Infinity and NaN = NaN
        if (isFinite(actual) || isFinite(expected)) {
            assert(Math.abs(actual - expected) <= epsilon,
                   "assert_approx_equals", description,
                   "expected ${expected} +/- ${epsilon} but got ${actual}",
                   {expected:expected, actual:actual, epsilon:epsilon});
        } else {
            assert_equals(actual, expected);
        }
    }
    expose_assert(assert_approx_equals, "assert_approx_equals");

    /**