Xunit: Analyzer to detect logging calls in tests

[marcind]

Based on #745, analyzer that detects calls to System.Console, System.Diagnostics.Debug, System.Diagnostics.Trace, and maybe others (System.Console.Error?). The fix provider would suggest using ITestOutputHelper (as per http://xunit.github.io/docs/capturing-output.html), including injecting it into the test class via constructor.

Things to consider:

• there are lots of variants of the Write/WriteLine methods, what would be the appropriate refactoring for each?
• when injecting the output helper, consider making sure that test class hierarchies still compile

[matkoch]

~@marcind I'm about to implement this. You can assign me if possible.~

~Some opinions/thoughts:~

• ~Should all invocations (no matter if Trace, Debug, Console) be redirected to ITestOutputHelper ? I think yes.~
• ~Fix can add a call to ToString() for all non-string literal types; or add additional methods on ITestOutputHelper. I would prefer ToString() calls.~
• ~Either add additional methods for Write, Write[Line]If; or add if statements when transforming; or don't provide a fix. I would prefer to not provide a fix; conditional test code is bad.~

Update: not of relevance anymore

[matkoch]

@marcind ping 😄

[AndreyAkinshin]

@marcind ping

[SimonCropp]

given the plan for v3 is to add Console / Trace / Debugger capture support perhaps this one should be closed?