chore: Cleaning up Auth integration tests (#239)

* chore: Cleaning up Auth integration tests

* fix: Added newline at the eof

Author: hiranya911

FirebaseAdmin/FirebaseAdmin.IntegrationTests/Auth/AbstractAuthFixture.cs

@@ -0,0 +1,34 @@
+// Copyright 2020, Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using FirebaseAdmin.Auth;
+
+namespace FirebaseAdmin.IntegrationTests.Auth
+{
+    /// <summary>
+    /// A fixture API that facilitates running the same set of integration tests on different
+    /// implementations of <c>AbstractFirebaseAuth</c>.
+    /// </summary>
+    public abstract class AbstractAuthFixture<T>
+    where T : AbstractFirebaseAuth
+    {
+        public abstract T Auth { get; }
+
+        public abstract TemporaryUserBuilder UserBuilder { get; }
+
+        public abstract string TenantId { get; }
+
+        public abstract T AuthFromApp(FirebaseApp app);
+    }
+}