chore(spanner): do not register backgroung begin txn in mock spanner

Author: harshachinta

google-cloud-spanner/src/main/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClient.java

@@ -316,7 +316,9 @@ private void verifyBeginTransactionWithRWOnMultiplexedSession(String sessionName
                 SessionImpl.createReadWriteTransactionOptions(
                     Options.fromTransactionOptions(), /* previousTransactionId = */ null))
             .setRequestOptions(
-                RequestOptions.newBuilder().setTransactionTag("multiplexed-rw-background-begin-txn").build());
+                RequestOptions.newBuilder()
+                    .setTransactionTag("multiplexed-rw-background-begin-txn")
+                    .build());
     final BeginTransactionRequest request = requestBuilder.build();
     final ApiFuture<Transaction> requestFuture;
     requestFuture =

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java

@@ -1872,7 +1872,10 @@ private Transaction getTemporaryTransactionOrNull(TransactionSelector tx) {
   @Override
   public void beginTransaction(
       BeginTransactionRequest request, StreamObserver<Transaction> responseObserver) {
-    if (!request.getRequestOptions().getTransactionTag().equals("multiplexed-rw-background-begin-txn")) {
+    if (!request
+        .getRequestOptions()
+        .getTransactionTag()
+        .equals("multiplexed-rw-background-begin-txn")) {
       requests.add(request);
     }
     Preconditions.checkNotNull(request.getSession());

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java

@@ -1341,16 +1341,6 @@ public void testInitialBeginTransactionWithRW_receivesUnimplemented_fallsBackToR
               return null;
             });
 
-    // Verify that we received one explicit BeginTransaction, and it uses a multiplexed session.
-    assertEquals(
-        mayBeIncrementBeginTransactionRequestsCount(spanner, /* count = */ 0),
-        mockSpanner.countRequestsOfType(BeginTransactionRequest.class));
-    List<BeginTransactionRequest> beginTxnRequests =
-        mockSpanner.getRequestsOfType(BeginTransactionRequest.class);
-    Session session1 = mockSpanner.getSession(beginTxnRequests.get(0).getSession());
-    assertNotNull(session1);
-    assertTrue(session1.getMultiplexed());
-
     // Verify that we received one ExecuteSqlRequest, and it uses a regular session due to fallback.
     List<ExecuteSqlRequest> executeSqlRequests =
         mockSpanner.getRequestsOfType(ExecuteSqlRequest.class);