chore: Add temporary workaround for ThreadingDiagnoserTests::CompletedWorkItemCountIsAccurate on macos (#3101)

* chore: add temporary workaround for #3098

* chore: modify precision logics

Author: filzrev

tests/BenchmarkDotNet.IntegrationTests/ThreadingDiagnoserTests.cs

@@ -55,7 +55,7 @@ public void CompletedWorkItemCountIsAccurate(IToolchain toolchain)
                 throw;
             }
 
-            AssertStats(summary, new Dictionary<string, (string metricName, double expectedValue)>
+            AssertStats(summary, toolchain, new Dictionary<string, (string metricName, double expectedValue)>
             {
                 { nameof(CompletedWorkItemCount.DoNothing), ("CompletedWorkItemCount", 0.0) },
                 { nameof(CompletedWorkItemCount.CompleteOneWorkItem), ("CompletedWorkItemCount", 1.0) }
@@ -96,7 +96,7 @@ public void LockContentionCountIsAccurate(IToolchain toolchain)
                 throw;
             }
 
-            AssertStats(summary, new Dictionary<string, (string metricName, double expectedValue)>
+            AssertStats(summary, toolchain, new Dictionary<string, (string metricName, double expectedValue)>
             {
                 { nameof(LockContentionCount.DoNothing), ("LockContentionCount", 0.0) },
                 { nameof(LockContentionCount.RunIntoLockContention), ("LockContentionCount", 1.0) }
@@ -167,7 +167,7 @@ private IConfig CreateConfig(IToolchain toolchain)
                     ? ConsoleLogger.Default
                     : new OutputLogger(output)); // we can't use OutputLogger for the InProcess toolchains because it allocates memory on the same thread
 
-        private void AssertStats(Summary summary, Dictionary<string, (string metricName, double expectedValue)> assertions)
+        private void AssertStats(Summary summary, IToolchain toolchain, Dictionary<string, (string metricName, double expectedValue)> assertions)
         {
             foreach (var assertion in assertions)
             {
@@ -177,7 +177,13 @@ private void AssertStats(Summary summary, Dictionary<string, (string metricName,
 
                 // precision is set to 2 because CoreCLR might schedule some work item on it's own and hence affect the results..
                 // precision = 3 is not enough (e.g., sometimes the actual value may be equal 1.0009765625 while the expected value is 1.0)
-                Assert.Equal(assertion.Value.expectedValue, metric.Value.Value, precision: 2);
+                int precision = 2;
+
+                // On macos, there are some additional background operations (https://github.com/dotnet/BenchmarkDotNet/issues/3098)
+                if (OsDetector.IsMacOS())
+                    precision = 1;
+
+                Assert.Equal(assertion.Value.expectedValue, metric.Value.Value, precision);
             }
         }
     }