This is some great work!

I've added a few comments for things to consider. Additionally, the build is failing because:

2018-12-09T20:27:55.4665359Z > [email protected] compile D:\a\1\s
2018-12-09T20:27:55.4665699Z > tsc -p .
2018-12-09T20:27:55.4665799Z
2018-12-09T20:27:55.4665923Z Tests/customReporterTest.ts(29,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666072Z Tests/emptyCollectionTest.ts(25,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666205Z Tests/emptyContents.ts(25,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666367Z Tests/emptyEnvironmentFile.ts(24,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666515Z Tests/emptyEnvironmentURL.ts(24,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666638Z Tests/folderTest.ts(29,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666793Z Tests/globalVarFileTest.ts(30,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4666919Z Tests/globalVarTest.ts(29,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4667041Z Tests/noEnvironment.ts(24,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4667180Z Tests/numberOfIterationTest.ts(29,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4667304Z Tests/useCollectionURL.ts(25,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4667449Z Tests/useEnvironmentFile.ts(30,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4667573Z Tests/useEnvironmentURL.ts(26,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4668726Z Tests/wrongCollectionURL.ts(25,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.
2018-12-09T20:27:55.4668884Z Tests/wrongEnvironmentURL.ts(25,9): error TS2339: Property 'stats' does not exist on type 'TaskLibAnswers'.

I haven't dug into why it cannot find stats yet.

I absolutely don't understand this error.... As my dev friend often says 'it works on my machine'.
I'll have a check if I can do sthg but I suspect a diff between my machine and build agent...

Definitely no idea about compilation issue. @carlowahlstedt can you please have a look ?

Finally it's OK ;-)

Not ignoring you here, just been really busy. I'll try to get back to looking at this over the weekend. I appreciate your work and patience on this.

So...hadn't really used the PR changes before. I had started comments days ago, but didn't realize I had to submit them before you could see them. Either way, they are there now.

Overall everything looks really good and I think your tests are probably a big testament to that. I'm thinking we will release this to a new major version (so people have to manually upgrade) since there are several potential breaking changes here.

Ok with your comments.
I applied them in PR #49...