How to use the expect.js.fail function in expect

it('fails when the value does not have a concat method', async () => {
      let promise;
      try {
        promise = createPromiseFromStreams([
          createListStream([1, '1']),
          createConcatStream()
        ]);
      } catch (err) {
        expect.fail('createPromiseFromStreams() should not fail synchronously');
      }

      try {
        await promise;
        expect.fail('Promise should have rejected');
      } catch (err) {
        expect(err).to.be.an(Error);
        expect(err.message).to.contain('concat');
      }
    });
  });

it('fails when the value does not have a concat method', async () => {
      let promise;
      try {
        promise = createPromiseFromStreams([
          createListStream([1, '1']),
          createConcatStream()
        ]);
      } catch (err) {
        expect.fail('createPromiseFromStreams() should not fail synchronously');
      }

      try {
        await promise;
        expect.fail('Promise should have rejected');
      } catch (err) {
        expect(err).to.be.an(Error);
        expect(err.message).to.contain('concat');
      }
    });
  });

spy.thisValues.forEach(function ($this) {
          if ($this.is(els.$scroller) || $this.is(els.$container)) return;
          expect.fail('expected ' + name + ' to be called with $scroller or $container');
        });
      }