A testing apparatus (100) for testing the position of a decorative piece (36) on a shell (32) includes a seat (10) and a board (20). A receiving space (144) is defined in the seat for receiving the shell. A measuring hole (22) defined in the board. The board is configured for engaging with the seat. The decorative piece is visible through the measuring hole when the board is attached to the seat. A pattern is disposed on the decorative piece. If the pattern is wholly visible through the measuring hole, the annular decorative piece is positioned correctly. If the pattern is not wholly visible through the measuring hole, the annular decorative piece is not positioned correctly.