public void AddRazorViewEngine_DoesNotReplaceExistingMetadataReferenceFeatureProvider()
        {
            // Arrange
            var services = new ServiceCollection();
            var builder  = services.AddMvcCore();
            var metadataReferenceFeatureProvider = new MetadataReferenceFeatureProvider();

            builder.PartManager.FeatureProviders.Add(metadataReferenceFeatureProvider);

            // Act
            builder.AddRazorViewEngine();

            // Assert
            var actual = Assert.Single(
                builder.PartManager.FeatureProviders.OfType <MetadataReferenceFeatureProvider>());

            Assert.Same(metadataReferenceFeatureProvider, actual);
        }
        public void AddRazorViewEngine_DoesNotReplaceExistingMetadataReferenceFeatureProvider()
        {
            // Arrange
            var services = new ServiceCollection();
            var builder  = services.AddMvcCore();

#pragma warning disable CS0618 // Type or member is obsolete
            var metadataReferenceFeatureProvider = new MetadataReferenceFeatureProvider();
#pragma warning restore CS0618 // Type or member is obsolete
            builder.PartManager.FeatureProviders.Add(metadataReferenceFeatureProvider);

            // Act
            builder.AddRazorViewEngine();

            // Assert
            var actual = Assert.Single(
#pragma warning disable CS0618 // Type or member is obsolete
                collection: builder.PartManager.FeatureProviders.OfType <MetadataReferenceFeatureProvider>());
#pragma warning restore CS0618 // Type or member is obsolete
            Assert.Same(metadataReferenceFeatureProvider, actual);
        }