Improve test coverage for RSAEncryptionPadding comparsion (#230)

* Improve test coverage for RSAEncryptionPadding comparsion

* Simplify RSASignaturePadding comparison logic

src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/RSASignaturePadding.cs

@@ -59,7 +59,7 @@ public override bool Equals(object obj)
 
         public bool Equals(RSASignaturePadding other)
         {
-            return other != null && _mode == other._mode;
+            return !object.ReferenceEquals(other, null) && _mode == other._mode;
         }
 
         public static bool operator ==(RSASignaturePadding left, RSASignaturePadding right)

src/libraries/System.Security.Cryptography.Algorithms/tests/RSATests.cs

@@ -193,9 +193,41 @@ public void VerifyDataStream_UsesHashDataAndVerifyHash()
         }
 
         [Fact]
-        public void RSAEncryptionPadding_Equals()
+        public void RSAEncryptionPadding_Equality()
         {
-            Assert.Equal(RSAEncryptionPadding.Pkcs1, RSAEncryptionPadding.Pkcs1);
+            Assert.True(RSAEncryptionPadding.Pkcs1.Equals(RSAEncryptionPadding.Pkcs1));
+            Assert.True(RSAEncryptionPadding.Pkcs1.Equals((object)RSAEncryptionPadding.Pkcs1));
+            Assert.True(RSAEncryptionPadding.Pkcs1 == RSAEncryptionPadding.Pkcs1);
+            Assert.False(RSAEncryptionPadding.Pkcs1 != RSAEncryptionPadding.Pkcs1);
+
+            Assert.False(RSAEncryptionPadding.Pkcs1.Equals(RSAEncryptionPadding.OaepSHA1));
+            Assert.False(RSAEncryptionPadding.Pkcs1.Equals((object)RSAEncryptionPadding.OaepSHA1));
+            Assert.False(RSAEncryptionPadding.Pkcs1 == RSAEncryptionPadding.OaepSHA1);
+            Assert.True(RSAEncryptionPadding.Pkcs1 != RSAEncryptionPadding.OaepSHA1);
+
+            Assert.False(RSAEncryptionPadding.Pkcs1.Equals(null));
+            Assert.False(RSAEncryptionPadding.Pkcs1.Equals((object)null));
+            Assert.False(RSAEncryptionPadding.Pkcs1 == null);
+            Assert.True(RSAEncryptionPadding.Pkcs1 != null);
+        }
+
+        [Fact]
+        public void RSASignaturePadding_Equality()
+        {
+            Assert.True(RSASignaturePadding.Pkcs1.Equals(RSASignaturePadding.Pkcs1));
+            Assert.True(RSASignaturePadding.Pkcs1.Equals((object)RSASignaturePadding.Pkcs1));
+            Assert.True(RSASignaturePadding.Pkcs1 == RSASignaturePadding.Pkcs1);
+            Assert.False(RSASignaturePadding.Pkcs1 != RSASignaturePadding.Pkcs1);
+
+            Assert.False(RSASignaturePadding.Pkcs1.Equals(RSASignaturePadding.Pss));
+            Assert.False(RSASignaturePadding.Pkcs1.Equals((object)RSASignaturePadding.Pss));
+            Assert.False(RSASignaturePadding.Pkcs1 == RSASignaturePadding.Pss);
+            Assert.True(RSASignaturePadding.Pkcs1 != RSASignaturePadding.Pss);
+
+            Assert.False(RSASignaturePadding.Pkcs1.Equals(null));
+            Assert.False(RSASignaturePadding.Pkcs1.Equals((object)null));
+            Assert.False(RSASignaturePadding.Pkcs1 == null);
+            Assert.True(RSASignaturePadding.Pkcs1 != null);
         }
 
         private sealed class EmptyRSA : RSA