diff --git a/velox/dwio/common/tests/MemorySinkTest.cpp b/velox/dwio/common/tests/MemorySinkTest.cpp
index b6f92ad32e76..fe4bfe5fb459 100644
--- a/velox/dwio/common/tests/MemorySinkTest.cpp
+++ b/velox/dwio/common/tests/MemorySinkTest.cpp
@@ -42,12 +42,14 @@ TEST_F(MemorySinkTest, create) {
   for (auto i = 10; i < chars.length(); ++i) {
     buffers.back().append(chars[i]);
   }
+
+  EXPECT_EQ(buffers.size(), 2);
+
   auto memorySink = std::make_unique<MemorySink>(
       1024, dwio::common::FileSink::Options{.pool = pool_.get()});
 
   ASSERT_TRUE(memorySink->isBuffered());
-  EXPECT_EQ(buffers.size(), 2);
-
+  // Write data to MemorySink.
   memorySink->write(buffers);
   EXPECT_EQ(memorySink->size(), chars.length());
   EXPECT_EQ(memorySink->data(), chars);