k and roll!
        source.start();

        context.startRendering()
            .then(function(result) {
              let expected = result.getChannelData(0);
              let actual = result.getChannelData(1);

              should(actual, '4-th order IIRFilter (biquad ref)')
                  .beCloseToArray(expected, {
                    // Thresholds experimentally determined.
                    absoluteThreshold: 1.59e-7,
                    relativeThreshold: 2.11e-5,
                  });

    