test: add tests to verify behavior of empty transactions (#1472)

Author: olavloite

src/test/java/com/google/cloud/spanner/jdbc/TransactionMockServerTest.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * 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 com.google.cloud.spanner.jdbc;
+
+import static org.junit.Assert.assertEquals;
+
+import com.google.cloud.spanner.connection.AbstractMockServerTest;
+import com.google.cloud.spanner.connection.SpannerPool;
+import com.google.spanner.v1.CommitRequest;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.sql.Statement;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class TransactionMockServerTest extends AbstractMockServerTest {
+
+  @AfterClass
+  public static void closeSpannerPool() {
+    SpannerPool.closeSpannerPool();
+  }
+
+  @After
+  public void clearRequests() {
+    mockSpanner.clearRequests();
+  }
+
+  private String createUrl() {
+    return String.format(
+        "jdbc:cloudspanner://localhost:%d/projects/%s/instances/%s/databases/%s?usePlainText=true;autoCommit=false",
+        getPort(), "proj", "inst", "db");
+  }
+
+  private Connection createConnection() throws SQLException {
+    return DriverManager.getConnection(createUrl());
+  }
+
+  @Test
+  public void testCommittingEmptyTransactionIsNoOp() throws SQLException {
+    try (Connection connection = createConnection()) {
+      connection.commit();
+    }
+
+    assertEquals(0, mockSpanner.countRequestsOfType(CommitRequest.class));
+  }
+
+  @Test
+  public void testCommittingEmptyExplicitTransactionIsNoOp() throws SQLException {
+    try (Connection connection = createConnection()) {
+      connection.setAutoCommit(true);
+      try (Statement statement = connection.createStatement()) {
+        statement.execute("begin transaction");
+        statement.execute("commit");
+      }
+    }
+
+    assertEquals(0, mockSpanner.countRequestsOfType(CommitRequest.class));
+  }
+
+  @Test
+  public void testRollingBackEmptyTransactionIsNoOp() throws SQLException {
+    try (Connection connection = createConnection()) {
+      connection.rollback();
+    }
+
+    assertEquals(0, mockSpanner.countRequestsOfType(CommitRequest.class));
+  }
+
+  @Test
+  public void testRollingBackEmptyExplicitTransactionIsNoOp() throws SQLException {
+    try (Connection connection = createConnection()) {
+      connection.setAutoCommit(true);
+      try (Statement statement = connection.createStatement()) {
+        statement.execute("begin transaction");
+        statement.execute("rollback");
+      }
+    }
+
+    assertEquals(0, mockSpanner.countRequestsOfType(CommitRequest.class));
+  }
+}