How to use the single-spa.NOT_MOUNTED function in single-spa

.then(() => {
        expect(parcel.getStatus()).toBe(singleSpa.NOT_MOUNTED);
      })
  });

.then(() => {
            expect(parcel.getStatus()).toBe(singleSpa.NOT_MOUNTED);
            expect(unmountPromiseHasResolved).toBe(false);

            return parcel
              .mountPromise
              .then(() => {
                expect(parcel.getStatus()).toBe(singleSpa.MOUNTED);
                expect(unmountPromiseHasResolved).toBe(false);
                expect(parcelConfig.bootstrapCalls).toBe(1);
                expect(parcelConfig.mountCalls).toBe(1);
                expect(parcelConfig.unmountCalls).toBe(0);

                shouldAppBeMounted = false;
                return singleSpa.triggerAppChange();
              })
          })
      })

      .then(() => expect(parcel.getStatus()).toBe(singleSpa.NOT_MOUNTED))
      .then(() => parcel.unmountPromise)

.then(() => {
        expect(parcel.getStatus()).toBe(singleSpa.NOT_MOUNTED);
        expect(app.unmountCalls).toBe(1);
      })
  });