Promise.all only accepts promises as parameters

[davidje13]

While debugging an issue in another project, I found that this mocking library doesn't conform to the spec for Promise.all

Specifically, Promise.all should be able to accept a mix of promises and non-promises, but https://github.com/charleshansen/mock-promises/blob/master/lib/mock-promises.js#L245 expects only promises.

Essentially:

const a = Promise.resolve('foo');
const b = 'bar';
const c = null;

Promise.all([a, b, c]).then(console.log);

Should print foo, bar, null. But currently it produces the error:

TypeError: promise.then is not a function

[charleshansen]

True story. I'm not 100% sure there even was a Promise.all spec when I wrote this. I don't know when I will have time to fix it, but I don't think it should be too bad. I'd gladly take a PR :)