avoid code duplication for disabling parallelization with xUnit

Author: adamsitnik

src/libraries/Common/tests/TestUtilities/System/DisableParallelization.cs

@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace System
+{
+    [CollectionDefinition(nameof(DisableParallelization), DisableParallelization = true)]
+    public class DisableParallelization { }
+}

src/libraries/Common/tests/TestUtilities/TestUtilities.csproj

@@ -18,6 +18,7 @@
     <Compile Include="System\AdminHelpers.cs" />
     <Compile Include="System\AssertExtensions.cs" />
     <Compile Include="System\IO\StreamExtensions.cs" />
+    <Compile Include="System\DisableParallelization.cs" />
     <Compile Include="System\RetryHelper.cs" />
     <Compile Include="System\Buffers\BoundedMemory.cs" />
     <Compile Include="System\Buffers\BoundedMemory.Creation.cs" />

src/libraries/System.ComponentModel.TypeConverter/tests/MemberDescriptorTests.cs

@@ -9,11 +9,8 @@
 
 namespace System.ComponentModel.Tests
 {
-    [CollectionDefinition("NoParallelTests", DisableParallelization = true)]
-    public partial class NoParallelTests { }
-
     // Mutable static comparision in the implementation
-    [Collection("NoParallelTests")]
+    [Collection(nameof(DisableParallelization))]
     public class MemberDescriptorTests
     {
         [Theory]

src/libraries/System.ComponentModel.TypeConverter/tests/ReflectionCachesUpdateHandlerTests.cs

@@ -7,7 +7,7 @@
 namespace System.ComponentModel.Tests
 {
     [SimpleUpdateTest]
-    [Collection("NoParallelTests")] // Clears the cache which disrupts concurrent tests
+    [Collection(nameof(DisableParallelization))] // Clears the cache which disrupts concurrent tests
     public class ReflectionCachesUpdateHandlerTests
     {
         [Fact]

src/libraries/System.ComponentModel.TypeConverter/tests/TypeDescriptorTests.cs

@@ -10,7 +10,7 @@
 
 namespace System.ComponentModel.Tests
 {
-    [Collection("NoParallelTests")] // manipulates cache
+    [Collection(nameof(DisableParallelization))] // manipulates cache
     public class TypeDescriptorTests
     {
         [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotMonoAOT))] // Mock will try to JIT 

src/libraries/System.IO.FileSystem.Watcher/tests/FileSystemWatcher.unit.cs

@@ -1086,7 +1086,7 @@ public void FileSystemWatcher_ModifyFiltersConcurrentWithEvents()
         }
     }
 
-    [Collection("NoParallelTests")]
+    [Collection(nameof(DisableParallelization))]
     public partial class DangerousFileSystemWatcherTests : FileSystemWatcherTest
     {
         private readonly ITestOutputHelper _output;

src/libraries/System.IO.FileSystem.Watcher/tests/Utility/FileSystemWatcherTest.cs

@@ -11,9 +11,6 @@
 
 namespace System.IO.Tests
 {
-    [CollectionDefinition("NoParallelTests", DisableParallelization = true)]
-    public partial class NoParallelTests { }
-
     public abstract partial class FileSystemWatcherTest : FileCleanupTestBase
     {
         // Events are reported asynchronously by the OS, so allow an amount of time for

src/libraries/System.IO.FileSystem/tests/FileStream/FileStreamConformanceTests.Windows.cs

@@ -77,7 +77,7 @@ protected override string GetTestFilePath(int? index = null, [CallerMemberName]
     }
 
     [PlatformSpecific(TestPlatforms.Windows)] // the test setup is Windows-specifc
-    [Collection("NoParallelTests")] // don't run in parallel, as file sharing logic is not thread-safe
+    [Collection(nameof(DisableParallelization))] // don't run in parallel, as file sharing logic is not thread-safe
     [OuterLoop("Requires admin privileges to create a file share")]
     [ConditionalClass(typeof(UncFilePathFileStreamStandaloneConformanceTests), nameof(CanShareFiles))]
     public class UncFilePathFileStreamStandaloneConformanceTests : UnbufferedAsyncFileStreamStandaloneConformanceTests

src/libraries/System.IO.FileSystem/tests/FileStream/ctor_options.cs

@@ -10,7 +10,7 @@ namespace System.IO.Tests
     // Don't run in parallel as the WhenDiskIsFullTheErrorMessageContainsAllDetails test
     // consumes entire available free space on the disk (only on Linux, this is how posix_fallocate works)
     // and if we try to run other disk-writing test in the meantime we are going to get "No space left on device" exception.
-    [Collection("NoParallelTests")]
+    [Collection(nameof(DisableParallelization))]
     public partial class FileStream_ctor_options : FileStream_ctor_str_fm_fa_fs_buffer_fo
     {
         protected override string GetExpectedParamName(string paramName) => "value";
@@ -166,7 +166,4 @@ public void WhenDiskIsFullTheErrorMessageContainsAllDetails(FileMode mode)
             Assert.False(exists);
         }
     }
-
-    [CollectionDefinition("NoParallelTests", DisableParallelization = true)]
-    public partial class NoParallelTests { }
 }

src/libraries/System.Net.Http/tests/FunctionalTests/SocketsHttpHandlerTest.Http2FlowControl.cs

@@ -11,16 +11,11 @@
 
 namespace System.Net.Http.Functional.Tests
 {
-    [CollectionDefinition(nameof(NonParallelTestCollection), DisableParallelization = true)]
-    public class NonParallelTestCollection
-    {
-    }
-
     // This test class contains tests which are strongly timing-dependent.
     // There are two mitigations avoid flaky behavior on CI:
     // - Parallel test execution is disabled
     // - Using extreme parameters, and checks which are very unlikely to fail, if the implementation is correct
-    [Collection(nameof(NonParallelTestCollection))]
+    [Collection(nameof(DisableParallelization))]
     [ConditionalClass(typeof(SocketsHttpHandler_Http2FlowControl_Test), nameof(IsSupported))]
     public sealed class SocketsHttpHandler_Http2FlowControl_Test : HttpClientHandlerTestBase
     {