message: adding effects tests
diff: import { expect } from "chai";
  import { BasicTests } from "test/helper/Basic";
  import { CompareToFile } from "test/helper/CompareToFile";
  +import { EffectTests } from "test/helper/EffectTests";
  import { Offline } from "test/helper/Offline";
  import { Oscillator } from "Tone/source/oscillator/Oscillator";
  import { FrequencyShifter } from "./FrequencyShifter";
  @@ -8,6 +9,7 @@ import { FrequencyShifter } from "./FrequencyShifter";
  describe("FrequencyShifter", () => {
  BasicTests(FrequencyShifter);
  + EffectTests(FrequencyShifter);
  it("matches a file", () => {
  return CompareToFile(() => {
  