Integrating Mocha unit test with fast-check results in unexpected behavior

[weilirs]

This is the Mocha test after integrating fast-check

it.only('should return an error when the user does not exist fuzzing', () => {
			return new Promise((resolve, reject) => {
				fc.assert(
					fc.property(
						fc.nat().map((randomString) => `lkajdfijain${randomString}`),
						(name) => {
							return new Promise((innerResolve, innerReject) => {
								request
									.get(api('users.info'))
									.set(credentials)
									.query({
										username: name,
									})
									.expect('Content-Type', 'application/json')
									.expect(400)
									.expect((res) => {
										console.log('res.body: ', res.body);
										expect(res.body).to.have.property('success', false);
										expect(res.body).to.have.property('error');
									})
									.end((err) => {
										if (err) {
											innerReject(err);
										} else {
											innerResolve();
										}
									});
							});
						},
					),
					{ verbose: true },
				)
					.then(resolve)
					.catch(reject); // Resolve or reject the outer promise based on the result of fc.assert
			});
		});

here in the console.log console.log('res.body: ', res.body);
It logs res.body: { success: false, error: 'User not found.' } which is expected but the test case ends up failing with unknown reason.

Any suggestions would be greatly appreciated!

[dubzzz]

Your test seem to be for an asynchronous piece of code, you should go for asyncProperty.

You might probably adapt it that way (I just replaced property by asyncProperty):

it.only('should return an error when the user does not exist fuzzing', () => {
  return new Promise((resolve, reject) => {
    fc.assert(
      fc.asyncProperty(
        fc.nat().map((randomString) => `lkajdfijain${randomString}`),
        (name) => {
          return new Promise((innerResolve, innerReject) => {
            request
              .get(api('users.info'))
              .set(credentials)
              .query({
                username: name,
              })
              .expect('Content-Type', 'application/json')
              .expect(400)
              .expect((res) => {
                console.log('res.body: ', res.body);
                expect(res.body).to.have.property('success', false);
                expect(res.body).to.have.property('error');
              })
              .end((err) => {
                if (err) {
                  innerReject(err);
                } else {
                  innerResolve();
                }
              });
          });
        }
      ),
      { verbose: true }
    )
      .then(resolve)
      .catch(reject); // Resolve or reject the outer promise based on the result of fc.assert
  });
});

Note: prefer async/await, it might drop some unneeded code.

[dubzzz]

Same with async/await would be:

it.only('should return an error when the user does not exist fuzzing', async () => {
  await fc.assert(
    fc.asyncProperty(
      fc.nat().map((randomString) => `lkajdfijain${randomString}`),
      async (name) => {
        return new Promise((innerResolve, innerReject) => {
          request
            .get(api('users.info'))
            .set(credentials)
            .query({
              username: name,
            })
            .expect('Content-Type', 'application/json')
            .expect(400)
            .expect((res) => {
              console.log('res.body: ', res.body);
              expect(res.body).to.have.property('success', false);
              expect(res.body).to.have.property('error');
            })
            .end((err) => {
              if (err) {
                innerReject(err);
              } else {
                innerResolve();
              }
            });
        });
      }
    ),
    { verbose: true }
  );
});

[weilirs]

thank you so much!!! It works!