Clean up tests under CoreMangLib/system/runtime/interopservices/safeh…

…andle (dotnet#58528)

* Delete redundant SafeHandle tests

* Move DangerousGetHandle and SetHandleAsInvalid tests to libraries

Remove IsClosed and SetHandle tests - covered by existing/new checks in
libraries tests.

src/libraries/System.Runtime.Handles/tests/SafeHandle.cs

@@ -40,25 +40,40 @@ public static void SafeHandle_invalid()
         Assert.False(mch.IsClosed);
         Assert.True(mch.IsInvalid);
         Assert.False(mch.IsReleased);
+        Assert.Equal(IntPtr.Zero, mch.DangerousGetHandle());
 
         mch.Dispose();
         Assert.True(mch.IsClosed);
         Assert.True(mch.IsInvalid);
         Assert.False(mch.IsReleased);
+
+        // Make sure we can dispose multiple times
+        mch.Dispose();
+        Assert.True(mch.IsClosed);
+        Assert.True(mch.IsInvalid);
+        Assert.False(mch.IsReleased);
     }
 
     [Fact]
     public static void SafeHandle_valid()
     {
-        MySafeHandle mch = new MySafeHandle(new IntPtr(1));
+        IntPtr ptr = new IntPtr(1);
+        MySafeHandle mch = new MySafeHandle(ptr);
         Assert.False(mch.IsClosed);
         Assert.False(mch.IsInvalid);
         Assert.False(mch.IsReleased);
+        Assert.Equal(ptr, mch.DangerousGetHandle());
 
         mch.Dispose();
         Assert.True(mch.IsClosed);
         Assert.False(mch.IsInvalid);
         Assert.True(mch.IsReleased);
+
+        // Make sure we can dispose multiple times
+        mch.Dispose();
+        Assert.True(mch.IsClosed);
+        Assert.False(mch.IsInvalid);
+        Assert.True(mch.IsReleased);
     }
 
     [Fact]
@@ -81,6 +96,18 @@ public static void SafeHandle_valid_close()
         Assert.True(mch.IsReleased);
     }
 
+    [Fact]
+    public static void SafeHandle_SetHandleAsInvalid()
+    {
+        IntPtr ptr = new IntPtr(1);
+        MySafeHandle handle = new MySafeHandle(ptr);
+        handle.SetHandleAsInvalid();
+        Assert.True(handle.IsClosed);
+        Assert.False(handle.IsInvalid);
+        Assert.False(handle.IsReleased);
+        Assert.Equal(ptr, handle.DangerousGetHandle());
+    }
+
     [DllImport("Kernel32", SetLastError = true)]
     private static extern void SetLastError(int error);