diff --git a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java
index 5986f92880..290583be1a 100644
--- a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java
+++ b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java
@@ -610,7 +610,9 @@ private static void checkStreamException(
   private ConcurrentMap<String, List<ByteString>> partitionTokens = new ConcurrentHashMap<>();
   private ConcurrentMap<ByteString, Instant> transactionLastUsed = new ConcurrentHashMap<>();
 
-  // Stores latest sequence number required for precommit token.
+  // Stores the latest sequence number needed for the precommit token.
+  // The transaction entry is created only if the transaction is read-write and executed on a
+  // multiplexed session.
   private static ConcurrentMap<ByteString, AtomicInteger> transactionSequenceNo =
       new ConcurrentHashMap<>();
   private int maxNumSessionsInOneBatch = 100;
diff --git a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java
index 7cb383a2d4..c7d7b697d6 100644
--- a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java
+++ b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java
@@ -926,7 +926,7 @@ public void testAbortedReadWriteTxnUsesPreviousTxnIdOnRetryWithExplicitBegin() {
             .getReadWrite()
             .getMultiplexedSessionPreviousTransactionId());
   }
-  
+
   @Test
   public void testPrecommitTokenForResultSet() {
     // This test verifies that the precommit token received from the ResultSet is properly tracked