Improve Update method to return ErrRecordNotFound if no rows were updated

ksql.go

@@ -541,9 +541,23 @@ func (c DB) Update(
 		return err
 	}
 
-	_, err = c.db.ExecContext(ctx, query, params...)
+	result, err := c.db.ExecContext(ctx, query, params...)
+	if err != nil {
+		return err
+	}
 
-	return err
+	n, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf(
+			"unexpected error: unable to fetch how many rows were affected by the update: %s",
+			err,
+		)
+	}
+	if n < 1 {
+		return ErrRecordNotFound
+	}
+
+	return nil
 }
 
 func buildInsertQuery(

ksql_test.go

@@ -1026,6 +1026,20 @@ func TestUpdate(t *testing.T) {
 				assert.Equal(t, 42, result.Age)
 			})
 
+			t.Run("should return ErrRecordNotFound when asked to update an inexistent user", func(t *testing.T) {
+				db := connectDB(t, driver)
+				defer db.Close()
+
+				ctx := context.Background()
+				c := newTestDB(db, driver)
+
+				err = c.Update(ctx, UsersTable, User{
+					ID:   4200,
+					Name: "Thayane",
+				})
+				assert.Equal(t, ErrRecordNotFound, err)
+			})
+
 			t.Run("should report database errors correctly", func(t *testing.T) {
 				db := connectDB(t, driver)
 				defer db.Close()