A kind of diagnostic tool that tests the integrity of circuits and the quality of electricity in computer components. It displays the information on an LCD or LED.?

The tool you're describing is likely a multimeter or a circuit tester, which assesses the integrity of electrical circuits and the quality of electrical signals in computer components. These devices typically feature an LCD or LED display to provide real-time readings of voltage, current, and resistance. They are essential for troubleshooting and diagnosing issues in electronic systems, ensuring components function correctly and efficiently.