Add test to verify the behavior of @DualDatabaseTest (#606)

core/src/test/java/google/registry/testing/DualDatabaseTestInvocationContextProviderTest.java

@@ -0,0 +1,54 @@
+// Copyright 2020 The Nomulus Authors. 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.
+
+package google.registry.testing;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.persistence.transaction.TransactionManagerFactory.tm;
+
+import google.registry.model.ofy.DatastoreTransactionManager;
+import google.registry.persistence.transaction.JpaTransactionManager;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.TestTemplate;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+/**
+ * Test to verify that {@link DualDatabaseTestInvocationContextProvider} extension executes {@link
+ * TestTemplate} test twice with different databases.
+ */
+@DualDatabaseTest
+public class DualDatabaseTestInvocationContextProviderTest {
+
+  private static int datastoreTestCounter = 0;
+  private static int postgresqlTestCounter = 0;
+
+  @RegisterExtension
+  public final AppEngineRule appEngine = AppEngineRule.builder().withDatastoreAndCloudSql().build();
+
+  @TestTemplate
+  void testToUseTransactionManager() {
+    if (tm() instanceof DatastoreTransactionManager) {
+      datastoreTestCounter++;
+    }
+    if (tm() instanceof JpaTransactionManager) {
+      postgresqlTestCounter++;
+    }
+  }
+
+  @AfterAll
+  static void assertEachTransactionManagerIsUsed() {
+    assertThat(datastoreTestCounter).isEqualTo(1);
+    assertThat(postgresqlTestCounter).isEqualTo(1);
+  }
+}