Add resolves() and rejects() method

[abdala]

Usually in other test libraries we have available the method resolves(value) to be alias to returns(Promise.resolve(value))

substitute.returnPromise().returns(Promise.resolve(1338));

becomes:

substitute.returnPromise().resolves(1338);

References:

• https://sinonjs.org/releases/v9.0.1/stubs/
• https://jestjs.io/docs/en/asynchronous#resolves--rejects

[ffMathy]

Minor changes needed. Good idea.

[ffMathy]

resolves should only be available functions that return promises.

[ffMathy]

Also, add documentation.

[abdala]

I'm not sure if this is the best implementation to restrict the method only for those that return a promise, but I'm open to suggestions.

[notanengineercom]

Really cool! Could you also implement in the same way rejects? With that we could have both promise results covered

[notanengineercom]

Nice how you refactored it! But I don't think it's a good idea to reassigning variables, I think something like this would be better:

Suggested change

	if (property === SubstituteMethods.resolves) {
	returns = returns.map(value => Promise.resolve(value))
	} else if(property === SubstituteMethods.rejects) {
	returns = returns.map(value => Promise.reject(value))
	}
	this.returns.push({
	returnValues: returns,
	returnIndex: 0,
	const returnMock: Partial<ReturnMock> = { returnIndex: 0, args: this._lastArgs };
	switch (property) {
	case SubstituteMethods.returns:
	returnMock.returnValues = returns;
	break;
	case SubstituteMethods.resolves:
	returnMock.returnValues = returns.map(value => Promise.resolve(value));
	break;
	case SubstituteMethods.rejects:
	returnMock.returnValues = returns.map(value => Promise.reject(value));
	break;
	default:
	throw SubstituteException.generic(
	`Expected one of the following methods: "${SubstituteMethods.returns}", "${SubstituteMethods.resolves}" or "${SubstituteMethods.rejects}"`
	);
	}
	this.returns.push(<ReturnMock>returnMock);

[abdala]

Nice! I just removed the default: throw from the code. It will never be reached in this case because of the if condition above :)

[notanengineercom]

True, the if prevents the default case. I added it in the suggestion for the future, in case new methods are added and the switch case doesn't get updated. It makes it easier to debug

[ffMathy]

If all tests pass, I'd say I have no more comments. Nicely done.

@notanengineercom when you are satisfied (and thanks for your review so far), feel free to merge.