fix(since): Retest all mutants covered by tests for which we cannot determine the filepath

src/Stryker.Core/Stryker.Core/MutantFilters/SinceMutantFilter.cs

@@ -1,13 +1,13 @@
 
+using System.Collections.Generic;
+using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.Extensions.Logging;
 using Stryker.Core.DiffProviders;
 using Stryker.Core.Logging;
 using Stryker.Core.Mutants;
 using Stryker.Core.Options;
 using Stryker.Core.ProjectComponents;
-using System.Collections.Generic;
-using System.Linq;
 
 namespace Stryker.Core.MutantFilters
 {
@@ -120,10 +120,13 @@ private IEnumerable<Mutant> ResetMutantStatusForChangedTests(IEnumerable<Mutant>
 
  foreach (var mutant in mutants)
  {
+ if (mutant.CoveringTests.IsEmpty || mutant.CoveringTests.Count == 0)
+ continue;
  var coveringTests = _tests.Extract(mutant.CoveringTests.GetGuids());
 
  if (coveringTests != null
- && coveringTests.Any(coveringTest => _diffResult.ChangedTestFiles.Any(changedTestFile => coveringTest.TestFilePath == changedTestFile)))
+ && coveringTests.Any(coveringTest => _diffResult.ChangedTestFiles.Any(changedTestFile => coveringTest.TestFilePath == changedTestFile
+ || string.IsNullOrEmpty(coveringTest.TestFilePath))))
  {
  mutant.ResultStatus = MutantStatus.Pending;
  mutant.ResultStatusReason = "One or more covering tests changed";

src/Stryker.Core/Stryker.Core/Mutants/TestSet.cs

@@ -20,6 +20,6 @@ public void RegisterTests(IEnumerable<TestDescription> tests)
 
  public void RegisterTest(TestDescription test) => _tests[test.Id] = test;
 
- public IEnumerable<TestDescription> Extract(IEnumerable<Guid> ids) => ids.Select(i => _tests[i]);
+ public IEnumerable<TestDescription> Extract(IEnumerable<Guid> ids) => ids?.Select(i => _tests[i]) ?? Enumerable.Empty<TestDescription>();
  }
 }