Sinon fake parameters aren't passed after 5.5.1

[edthorne]

This is related to the fix applied for #256. I spent some time upgrading through releases to find the behavior was working through version 5.5.0 and stopped working with 5.5.1. This may or may not be related to #273.

In my case I was using a fake to implement behavior as follows:

const awsSdkMock = require('aws-sdk-mock')
const AWS = require('aws-sdk')
const { describe, it, beforeEach, afterEach } = require('mocha')
const { expect } = require('chai')
const sinon = require('sinon')

describe('Test case', () => {
    beforeEach(() => {
        awsSdkMock.setSDKInstance(AWS);
    });

    afterEach(() => {
        awsSdkMock.restore();
        sinon.restore();
    })

    it('should be able to access parameters', async () => {
        // use a fake to mock behavior (works < 5.5.1)
        const createDBSnapshotMock = sinon.fake(params => {
            // return the passed in identifier in the response
            return Promise.resolve({ DBSnapshot: { DBSnapshotIdentifier: params.DBSnapshotIdentifier } })
        })
        awsSdkMock.mock('RDS', 'createDBSnapshot', createDBSnapshotMock)

        const rds = new AWS.RDS()

        const result = await rds.createDBSnapshot({
            DBInstanceIdentifier: 'dbInstanceId',
            DBSnapshotIdentifier: 'snapshotId'
        }).promise()

        expect(createDBSnapshotMock.callCount).to.equal(1)
        expect(createDBSnapshotMock.firstCall.args[0].DBSnapshotIdentifier)
            .to.equal('snapshotId')
        expect(result.DBSnapshot.DBSnapshotIdentifier).to.equal('snapshotId');
    })
});

The changes in #257 result in the constructed callback spy being passed as the parameters to the fake rather than the parameters to the mocked function.

If I change the fake to accept an extra, unused parameter like this: const createDBSnapshotMock = sinon.fake((params, cb) => { then it results in the parameters being passed as expected since replace.length === 2.

I'm not sure what the proper behavior is in this case and if the second argument for the fake parameters is required.

[edthorne]

I have a second related issue where I'm using a fake to prevent the SDK from executing a call during testing.

    // service mock to prevent notification callout
    AWS.mock('SNS', 'publish', sinon.fake())

The fake provides no return value/undefined so typeof result.then logs an error. This tracks back to the changes in #253. The issue does not occur on 5.4.0.