Fix test case to properly wait for all queries to be pending.

Signed-off-by: Arthur Schreiber <[email protected]>

go/vt/vttablet/tabletserver/tabletserver_test.go

@@ -1122,6 +1122,20 @@ func TestSerializeTransactionsSameRow_ConcurrentTransactions(t *testing.T) {
 	db.SetBeforeFunc("update test_table set name_string = 'tx1' where pk = 1 and `name` = 1 limit 10001",
 		func() {
 			close(tx1Started)
+
+			// Wait for other queries to be pending.
+			<-allQueriesPending
+		})
+
+	db.SetBeforeFunc("update test_table set name_string = 'tx2' where pk = 1 and `name` = 1 limit 10001",
+		func() {
+			// Wait for other queries to be pending.
+			<-allQueriesPending
+		})
+
+	db.SetBeforeFunc("update test_table set name_string = 'tx3' where pk = 1 and `name` = 1 limit 10001",
+		func() {
+			// Wait for other queries to be pending.
 			<-allQueriesPending
 		})
 
@@ -1190,6 +1204,8 @@ func TestSerializeTransactionsSameRow_ConcurrentTransactions(t *testing.T) {
 	// to allow more than connection attempt at a time.
 	err := waitForTxSerializationPendingQueries(tsv, "test_table where pk = 1 and `name` = 1", 3)
 	require.NoError(t, err)
+
+	// Signal that all queries are pending now.
 	close(allQueriesPending)
 
 	wg.Wait()