add failing test case for singleton generator with switch

Author: bert2

test/coverlet.core.tests/Coverage/CoverageTest.Yield.cs

@@ -30,6 +30,7 @@ public void Yield_Single()
                 CoverageResult result = TestInstrumentationHelper.GetCoverageResult(path);
 
                 result.Document("Instrumentation.Yield.cs")
+                      .Method("System.Boolean Coverlet.Core.Samples.Tests.Yield/<One>d__0::MoveNext()")
                       .AssertLinesCovered((9, 1))
                       .ExpectedTotalNumberOfBranches(0);
             }
@@ -59,6 +60,7 @@ public void Yield_Multiple()
                 CoverageResult result = TestInstrumentationHelper.GetCoverageResult(path);
 
                 result.Document("Instrumentation.Yield.cs")
+                      .Method("System.Boolean Coverlet.Core.Samples.Tests.Yield/<Two>d__1::MoveNext()")
                       .AssertLinesCovered((14, 1), (15, 1))
                       .ExpectedTotalNumberOfBranches(0);
             }
@@ -67,5 +69,36 @@ public void Yield_Multiple()
                 File.Delete(path);
             }
         }
+
+        [Fact]
+        public void Yield_SingleWithSwitch()
+        {
+            string path = Path.GetTempFileName();
+            try
+            {
+                FunctionExecutor.Run(async (string[] pathSerialize) =>
+                {
+                    CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Yield>(instance =>
+                    {
+                        foreach (var _ in instance.OneWithSwitch(2)) ;
+
+                        return Task.CompletedTask;
+                    }, persistPrepareResultToFile: pathSerialize[0]);
+
+                    return 0;
+                }, new string[] { path });
+
+                CoverageResult result = TestInstrumentationHelper.GetCoverageResult(path);
+
+                result.Document("Instrumentation.Yield.cs")
+                      .Method("System.Boolean Coverlet.Core.Samples.Tests.Yield/<OneWithSwitch>d__2::MoveNext()")
+                      .AssertLinesCovered((30, 1), (31, 1), (37, 1))
+                      .ExpectedTotalNumberOfBranches(1);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
     }
 }

test/coverlet.core.tests/Coverage/InstrumenterHelper.Assertions.cs

@@ -79,6 +79,36 @@ public static Document Document(this CoverageResult coverageResult, string docNa
             throw new XunitException($"Document not found '{docName}'");
         }
 
+        public static Document Method(this Document document, string methodName)
+        {
+            var methodDoc = new Document { Path = document.Path, Index = document.Index };
+
+            if (!document.Lines.Any() && !document.Branches.Any())
+            {
+                return methodDoc;
+            }
+
+            if (document.Lines.Values.All(l => l.Method != methodName) && document.Branches.Values.All(l => l.Method != methodName))
+            {
+                var methods = document.Lines.Values.Select(l => $"'{l.Method}'")
+                    .Concat(document.Branches.Values.Select(b => $"'{b.Method}'"))
+                    .Distinct();
+                throw new XunitException($"Method '{methodName}' not found. Methods in document: {string.Join(", ", methods)}");
+            }
+
+            foreach (var line in document.Lines.Where(l => l.Value.Method == methodName))
+            {
+                methodDoc.Lines[line.Key] = line.Value;
+            }
+
+            foreach (var branch in document.Branches.Where(b => b.Value.Method == methodName))
+            {
+                methodDoc.Branches[branch.Key] = branch.Value;
+            }
+
+            return methodDoc;
+        }
+
         public static Document AssertBranchesCovered(this Document document, params (int line, int ordinal, int hits)[] lines)
         {
             return AssertBranchesCovered(document, BuildConfiguration.Debug | BuildConfiguration.Release, lines);

test/coverlet.core.tests/Samples/Instrumentation.Yield.cs

@@ -14,5 +14,27 @@ public System.Collections.Generic.IEnumerable<int> Two()
             yield return 1;
             yield return 2;
         }
+
+        public System.Collections.Generic.IEnumerable<int> OneWithSwitch(int n)
+        {
+            int result;
+            switch (n)
+            {
+                case 0:
+                    result = 10;
+                    break;
+                case 1:
+                    result = 11;
+                    break;
+                case 2:
+                    result = 12;
+                    break;
+                default:
+                    result = -1;
+                    break;
+            }
+
+            yield return result;
+        }
     }
 }