avoid test flakeness caused by static field

Author: yugangw-msft

src/Common/Commands.Common.Test/Common/ProfileCmdltsTests.cs

@@ -152,9 +152,15 @@ public void ClearAzureProfileClearsTokenCache()
         [Fact]
         public void DeleteCorruptedTokenCache()
         {
-            ProfileClient.DataStore.WriteFile(ProtectedFileTokenCache.CacheFileName, new byte[]{0,1});
-            ProtectedFileTokenCache tokenCache = ProtectedFileTokenCache.Instance;
-            Assert.False(ProfileClient.DataStore.FileExists(ProtectedFileTokenCache.CacheFileName));
+            //setup
+            string testFileName = @"c:\foobar\TokenCache.dat";
+            ProfileClient.DataStore.WriteFile(testFileName, new byte[] { 0, 1 });
+            
+            //Act
+            ProtectedFileTokenCache tokenCache = new ProtectedFileTokenCache(testFileName);
+
+            //Assert
+            Assert.False(ProfileClient.DataStore.FileExists(testFileName));
         }
 
         [Fact]

src/Common/Commands.Common/Authentication/ProtectedFileTokenCache.cs

@@ -26,7 +26,7 @@ namespace Microsoft.WindowsAzure.Commands.Utilities.Common.Authentication
     /// </summary>
     public class ProtectedFileTokenCache : TokenCache
     {
-        public static readonly string CacheFileName = Path.Combine(AzurePowerShell.ProfileDirectory, "TokenCache.dat");
+        private static readonly string CacheFileName = Path.Combine(AzurePowerShell.ProfileDirectory, "TokenCache.dat");
 
         private static readonly object fileLock = new object();
 
@@ -44,29 +44,39 @@ public static ProtectedFileTokenCache Instance
         // Initializes the cache against a local file.
         // If the file is already present, it loads its content in the ADAL cache
         private ProtectedFileTokenCache()
+        {
+            Initialize(CacheFileName);
+        }
+
+        private void Initialize(string fileName)
         {
             AfterAccess = AfterAccessNotification;
             BeforeAccess = BeforeAccessNotification;
             lock (fileLock)
             {
-                if (ProfileClient.DataStore.FileExists(CacheFileName))
+                if (ProfileClient.DataStore.FileExists(fileName))
                 {
-                    var existingData = ProfileClient.DataStore.ReadFileAsBytes(CacheFileName);
+                    var existingData = ProfileClient.DataStore.ReadFileAsBytes(fileName);
                     if (existingData != null)
                     {
                         try
                         {
                             Deserialize(ProtectedData.Unprotect(existingData, null, DataProtectionScope.CurrentUser));
                         }
-                        catch (CryptographicException) 
+                        catch (CryptographicException)
                         {
-                            ProfileClient.DataStore.DeleteFile(CacheFileName);
+                            ProfileClient.DataStore.DeleteFile(fileName);
                         }
                     }
                 }
             }
         }
 
+        public ProtectedFileTokenCache(string cacheFile)
+        {
+            Initialize(cacheFile);
+        }
+
         // Empties the persistent store.
         public override void Clear()
         {