test(itest): cover the immediate read-then-write upgrade

libsql-itests/src/test/java/io/github/magnusp/libsql/itest/TransactionModeIT.java

@@ -7,11 +7,17 @@
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.Statement;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 
 import static io.github.magnusp.libsql.itest.SqldTransactionSupport.assertWriteIsBlockedUntilReleased;
 import static io.github.magnusp.libsql.itest.SqldTransactionSupport.createTable;
 import static io.github.magnusp.libsql.itest.SqldTransactionSupport.insertRow;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 public class TransactionModeIT extends SqldContainerBase {
 
@@ -33,6 +39,50 @@ void urlImmediateTransactionModeHoldsTheWriteLockFromTheFirstStatement() throws
         }
     }
 
+    @Test
+    void urlImmediateTransactionModeUpgradesAReadToAWriteAndCommitsWhileAWriterWaits()
+            throws Exception {
+        String url = "jdbc:libsql:" + getHttpUrl() + "?transactionMode=immediate";
+        try (Connection transaction = DriverManager.getConnection(url);
+             Statement statement = transaction.createStatement()) {
+            createTable(transaction, "url_immediate_read_write");
+            transaction.setAutoCommit(false);
+            try (ResultSet rows =
+                    statement.executeQuery("SELECT COUNT(*) FROM url_immediate_read_write")) {
+                assertThat(rows.next()).isTrue();
+            }
+
+            ExecutorService executor = Executors.newSingleThreadExecutor();
+            try {
+                Future<Integer> waitingWriter = executor.submit(() -> {
+                    try (Connection writer = DriverManager.getConnection(url)) {
+                        return insertRow(writer, "url_immediate_read_write", 1);
+                    }
+                });
+                assertThatThrownBy(() -> waitingWriter.get(300, TimeUnit.MILLISECONDS))
+                        .as("immediate takes the write lock at the read, so the writer waits")
+                        .isInstanceOf(TimeoutException.class);
+
+                assertThat(statement.executeUpdate(
+                                "INSERT INTO url_immediate_read_write (id) VALUES (2)"))
+                        .isEqualTo(1);
+                transaction.commit();
+
+                assertThat(waitingWriter.get(20, TimeUnit.SECONDS)).isEqualTo(1);
+            } finally {
+                executor.shutdownNow();
+            }
+        }
+
+        try (Connection verifier = DriverManager.getConnection(url);
+             Statement statement = verifier.createStatement();
+             ResultSet rows =
+                     statement.executeQuery("SELECT COUNT(*) FROM url_immediate_read_write")) {
+            assertThat(rows.next()).isTrue();
+            assertThat(rows.getInt(1)).isEqualTo(2);
+        }
+    }
+
     @Test
     void urlDeferredTransactionModeDoesNotHoldTheWriteLockFromTheFirstStatement() throws Exception {
         String url = "jdbc:libsql:" + getHttpUrl() + "?transactionMode=deferred";