added unit test for additional failure cases and removed unneeded code from existing unit tests

src/ps_test/test_CorePsPlatform.cs

@@ -102,6 +102,7 @@ namespace PSTests
             {
                 File.Create(path);
             }
+
             // Create a file to write to using StreamWriter. 
             // convert string to stream.  On Windows, this appears to be handled, but on *nix, we apparently need to convert to UTF8.
             byte[] byteArray    = System.Text.Encoding.UTF8.GetBytes(path);
@@ -123,16 +124,23 @@ namespace PSTests
             // A folder that should exist on every *nix system
             string path = @"/tmp";
 
-            // Create a file to write to using StreamWriter. 
-            // convert string to stream.  On Windows, this appears to be handled, but on *nix, we apparently need to convert to UTF8.
-            byte[] byteArray    = System.Text.Encoding.UTF8.GetBytes(path);
-            MemoryStream stream = new MemoryStream(byteArray);
+            // Convert `path` string to FileSystemInfo data type. And now, it should return true
+            FileSystemInfo fd = new FileInfo(path);
+            Assert.False(Platform.NonWindowsIsHardLink(fd));
+        }
+
+        [Fact]
+        public static void TestIsHardLinkFailsWithNonexistantFileWithFileSystemInfo()
+        {
+            // A file that should *never* exist on a test machine:
+            string path = @"/tmp/ThisFileShouldNotExistOnTestMachines";
+
+            // If the file exists, then there's a larger issue that needs to be looked at
+            Assert.False(File.Exists(path));
 
             // Convert `path` string to FileSystemInfo data type. And now, it should return true
             FileSystemInfo fd = new FileInfo(path);
             Assert.False(Platform.NonWindowsIsHardLink(fd));
-
         }
-
     }
 }