diff --git a/pbm/oplog/db_test.go b/pbm/oplog/db_test.go
new file mode 100644
index 000000000..69938ae85
--- /dev/null
+++ b/pbm/oplog/db_test.go
@@ -0,0 +1,56 @@
+package oplog
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/mongo/integration/mtest"
+)
+
+func TestGetUUIDForNS(t *testing.T) {
+	mt := mtest.New(t, mtest.NewOptions().ClientType(mtest.Mock))
+
+	mt.Run("successful response from db", func(mt *mtest.T) {
+		expectedUUID := primitive.Binary{Subtype: 0xFF, Data: []byte{0x01, 0x02, 0x03}}
+		listCollRes := bson.D{
+			{"name", "c1"},
+			{"type", "collection"},
+			{"info", bson.D{
+				{"readOnly", false},
+				{"uuid", expectedUUID},
+			}}}
+		mt.AddMockResponses(mtest.CreateCursorResponse(1, "mydb.c1", mtest.FirstBatch, listCollRes))
+
+		db := newMDB(mt.Client)
+		uuid, err := db.getUUIDForNS(context.Background(), "mydb.c1")
+		if err != nil {
+			t.Errorf("got err=%v", err)
+		}
+		primitive.NewObjectID()
+
+		if !uuid.Equal(expectedUUID) {
+			t.Errorf("wrong uuid for ns: expected=%v, got=%v", expectedUUID, uuid)
+		}
+		t.Log(uuid)
+	})
+
+	mt.Run("failed response from db", func(mt *mtest.T) {
+		errRes := mtest.CreateCommandErrorResponse(mtest.CommandError{
+			Code:    11601,
+			Name:    "error",
+			Message: "querying list collections",
+		})
+		mt.AddMockResponses(errRes)
+		db := newMDB(mt.Client)
+		_, err := db.getUUIDForNS(context.Background(), "mydb.c1")
+		if err == nil {
+			t.Error("expected to get error from getUUIDForNS")
+		}
+		if !strings.Contains(err.Error(), "list collections") {
+			t.Error("wrong err")
+		}
+	})
+}