message: chore(test): fix bufferWhen types
diff: @@ -15,7 +15,7 @@ describe('bufferWhen operator', () => {
  const values = {
  x: ['b', 'c', 'd'],
  y: ['e', 'f', 'g'],
  - z: []
  + z: [] as string[]
  };
  expectObservable(e1.pipe(bufferWhen(() => e2))).toBe(expected, values);
  @@ -239,7 +239,7 @@ describe('bufferWhen operator', () => {
  const e1subs = '(^!)';
  const expected = '(x|)';
  const values = {
  - x: []
  + x: [] as string[]
  };
  const result = e1.pipe(bufferWhen(() => e2));
  @@ -254,7 +254,7 @@ describe('bufferWhen operator', () => {
  const e1subs = '(^!)';
  const expected = '#';
  const values = {
  - x: []
  + x: [] as string[]
  };
  const result = e1.pipe(bufferWhen(() => e2));
  @@ -276,7 +276,7 @@ describe('bufferWhen operator', () => {
  ' ^ !'];
  const expected = '--------x-------x-------x-------x-------x----';
  const values = {
  - x: []
  + x: [] as string[]
  };
  const source = e1.pipe(bufferWhen(() => e2));
  @@ -346,7 +346,7 @@ describe('bufferWhen operator', () => {
  const values = {
  x: ['b', 'c', 'd'],
  y: ['e', 'f', 'g', 'h'],
  - z: []
  + z: [] as string[]
  };
  const source = e1.pipe(bufferWhen(() => e2));
  