Code coverage using dotCover throws an error - FAK

Question

I am trying to use DotCover in FAKE , but it is throwing some error , as I am new to FAKE as well as F# , it's becoming difficult for me to understand the root cause of the problem . Here is the code :

 #r "D:/FAKEProject/Fake/packages/FAKE/tools/FakeLib.dll"
    open Fake
    open Fake.DotCover
    let testDir = "D:/FAKEProject/Fake/test/"
    let filters = ""
    Target "Clean" (fun _ ->
        CleanDirs [testDir]
    )
    Target "TestCoverage" (fun _ ->
        !! ("D:/FAKEProject/Fake/UnitTest/UnitTest.dll")
            |> DotCoverNUnit
                (fun p -> { p with Output = testDir @@ "NUnitDotCover.snapshot"
                                   ToolPath = "D:/tools/dotCover/dotCover.exe"
                                   Filters = filters })                              
                (fun nunitOptions -> nunitOptions)
    )
    "Clean"
        ==> "TestCoverage"
    RunTargetOrDefault "TestCoverage"`

It is giving this error

System.Exception: Error running D:/tools/dotCover/dotCover.exe with exitcode -1
   at [e-mail](String message) in C:\code\fake\src\app\FakeLib\DotCover.fs:line 124
   at Fake.DotCover.buildParamsAndExecute[a](a parameters, FSharpFunc`2 buildArguments, String toolPath, String workingDir, Boolean failBuild) in C:\code\fake\src\app\FakeLib\DotCover.fs:line 124
   at Fake.DotCover.DotCoverNUnit(FSharpFunc`2 setDotCoverParams, FSharpFunc`2 setNUnitParams, IEnumerable`1 assemblies) in C:\code\fake\src\app\FakeLib\DotCover.fs:line 190
   at [e-mail](Unit _arg2) in D:\FAKEProject\Fake\DotCover.fsx:line 17
   at Fake.TargetHelper.runSingleTarget(TargetTemplate`1 target) in C:\code\fake\src\app\FakeLib\TargetHelper.fs:line 492`

I am not able to understand why it is searching in C:\code\fake\src\app\fakelib\dotcover.fs and what is dotcover.fs it is looking for How to solve this problem , as I am stuck at this error , If anyone can help me regarding this , it would be very helpful .

Thank You

Answer 1

The mysterious C:\code\fake\src\app\FakeLib\DotCover.fs line is simply telling you the filename (and line number) of the source file that threw the error. Not the filename on your system, but the filename on the system where your FAKE.exe file was built. In other words, it's just telling you where the exception was thrown from.

Looking at the FAKE source code, I see that line 124 is near the end of the following block of code:

let buildParamsAndExecute parameters buildArguments toolPath workingDir failBuild =
    let args = buildArguments parameters
    trace (toolPath + " " + args)
    let result = ExecProcess (fun info ->  
              info.FileName <- toolPath
              info.WorkingDirectory <- getWorkingDir workingDir
              info.Arguments <- args) TimeSpan.MaxValue
    let ExitCodeForFailedTests = -3
    if (result = ExitCodeForFailedTests && not failBuild) then 
        trace (sprintf "DotCover %s exited with errorcode %d" toolPath result)
    else if (result = ExitCodeForFailedTests && failBuild) then 
        failwithf "Failing tests, use ErrorLevel.DontFailBuild to ignore failing tests. Exited %s with errorcode %d" toolPath result
    else if (result <> 0) then 
        failwithf "Error running %s with exitcode %d" toolPath result
    else 
        trace (sprintf "DotCover exited successfully")

The failwithf function is F#'s equivalent of "throw new Exception()", but it lets you specify a message (using printfn-style format codes like %s) to go with the exception. So there's nothing mysterious going on here in F#, it's just that your D:/tools/dotCover/dotCover.exe program has returned a -1 return code. Return codes of -1 usually mean "generic error", so that's not much help in figuring out the cause.

Your next troubleshooting step is to run your dotCover.exe program manually, giving it the same arguments that FAKE is giving it (shouldn't be too hard to figure out, since the FAKE option records are usually pretty well-named) and the same input. Then see what error messages, if any, dotCover.exe is printing out before it fails.