A cable tester is a network troubleshooting tool used to test network cables. A cable tester can test the continuity and quality of network cables by sending signals through the cable and measuring the response. A cable tester can detect common cable faults, such as open circuits, short circuits, and miswires. Cable testers can also identify the type and speed of network cables, such as Cat5, Cat6, or fiber optic cables. Cable testers are essential for ensuring the reliability and performance of network infrastructure.