There are some points which indicate that testing is complete:

1-The exit criteria that was mentioned in the test plan document is achieved.

2-when we acheived no. of successful test case execution at a specified level.

2-when rate of bug finding decrease from a specified level.

3-when manager said that ok stop.

4-when we dont have enough time to perform more test and have acheived a specified level of quality.

5-when the cost of fixing a bug ismore then the impact of the bug in the system.