Potential problem with coverage analysis on async tests

//First Scenario
[HttpPut("api/myendpoint01")]
public async Task<IActionResult> MyEndPoint01(string param)
{
 //Here the mutant is killed
 if(string.IsNullOrEmpty(param))
 {
   //Do something...
   return BadRequest();
 }
 //.......
}
//Second Scenario
[HttpPut("api/myendpoint02")]
public async Task<IActionResult> MyEndPoint02(string param)
{
 //Here the mutant is survived
 if(string.IsNullOrEmpty(param))
 {
   //Do something...
   return BadRequest();
 }

 //....... 
 
}

I’ve got the unit test for both endpoint covering the BadRequest result and Ok result.

My question is why in the first scenario the mutant is killed but in the second one it is survived?

Info:

Windows 10 Pro .NET Core 2.1.509 NUnit 3.12.0 Stryker 0.18.0

[dupdob]

Thanks @Mobrockers : I was about to say the same thing here. It sounds like a coverage issue. I lack experience with tests marked as ‘async’ but those could potentially result in invalid coverage data.

[rodrigogurgel]

Try it dotnet stryker -tr dotnettest