Function callback

test/waveform-builder-spec.js:361–365

(err, waveformData)

      const waveformBuilder = new WaveformBuilder(peaks);

      function callback(err, waveformData) {
        expect(err).to.be.an.instanceOf(Error);
        expect(waveformData).to.equal(undefined);
        done();
      }

      waveformBuilder.init(peaks.options, callback);
      waveformBuilder.abort();