如何以开玩笑的角度模拟承诺？

Question

Here is the method I have:

  async signMessage(xml, mbo): Promise<any> {
    try {
      const isSignatureAppAlive = await this.pingDigitalSignatureApp().toPromise();
 
      if (isSignatureAppAlive.alive) {
        try {
          this.signedMsg = await this.getSignedMsg(xml, mbo).toPromise();
          return this.signedMsg;
        } catch (er) {
          return this.handleSignatureAppErrorCodes(er.error.errorCode);
        }
      }
    } catch (e) {
      this.showSignatureInfoModal();
      return this.handleError({ message: 'empty' });
    }
  }

getSignedMsg(msg, mbo): Observable<any> {
    this.signDocument.title = '';
    this.signDocument.content = btoa(msg);
    this.signDocument.contentType = 'application/xml';
    this.signDocument.uriOrIdToSign = '';

    this.postParam.certificateAlias = mbo;
    this.postParam.digestAlgorithm = 'SHA1';
    this.postParam.documents = [];
    this.postParam.documents.push(this.signDocument);
    this.postParam.signingMethod = 'xmldsig';
    this.postParam.envelopingMethod = 'enveloped';

    return this.http.post<any>(SERVICE_URL + 'sign', this.postParam, httpOptions).pipe();
  }

My test covers catching error:

   service.signMessage('xml', 'mbo').catch((errCode) => {
     expect(errCode).toBe('empty');
     done();
   });
 });

What logic do I need to add in order to cover if statement? Do I have to mock a Promise? Not sure what to do here. I tried this:

  it('signMessage', async (done) => {
    const spy = spyOn(service, 'pingDigitalSignatureApp').and.returnValue(
      new Promise((resolve) => resolve('someVal')),
    );
    service.pingDigitalSignatureApp();
    expect(spy).toHaveBeenCalled();
    done();
  });

Nothing happens, in a sense that test doesn't go to if statement. Advice appreciated.

Answer 1

Since you're doing a .toPromise() on the method in question, you need to return an Observable and not a promise. And yes, you need to return an object where the if condition will be satisfied.

Try this:

// we don't need done
it('signMessage', async () => {
    // return an observable
    const spy = spyOn(service, 'pingDigitalSignatureApp').and.returnValue(
      of({ alive: true } as any) 
    );
    // make getSignedMsg return hello
    spyOn(service, 'getSignedMsg').and.returnValue(of('hello'));
    // await for the result
    const result = await service.pingDigitalSignatureApp();
    expect(spy).toHaveBeenCalled();
    // expect it to go inside of the if and it returned hello
    expect(result).toBe('hello');
  });