add support for .NET Framework

Author: fgreinacher

.github/workflows/ci.yml

@@ -18,7 +18,12 @@ jobs:
         with:
           fetch-depth: 0
       - name: Run tests
-        run: dotnet test --verbosity normal --collect:"XPlat Code Coverage"
+        run: dotnet test --collect:"XPlat Code Coverage"
+      - name: Upload snapshots
+        uses: actions/upload-artifact@v2
+        with:
+          name: Snapshots ${{ matrix.os }}
+          path: "**/*.snap"
       - name: Upload coverage
         uses: actions/upload-artifact@v2
         with:

tests/System.IO.Abstractions.Tests/ApiCompletenessTests.cs

@@ -97,6 +97,8 @@ public ApiDiff(IEnumerable<string> extraMembers, IEnumerable<string> missingMemb
         private const string snapshotSuffix = ".NET Core 3.1";
 #elif NETCOREAPP2_1
             private const string snapshotSuffix = ".NET Core 2.1";
+#elif NET461
+            private const string snapshotSuffix = ".NET Framework 4.6.1";
 #else
 #error Unknown target framework.
 #endif