Intrusive testing can be considered a type of interrupt testing, which is used to test how well a system reacts to intrusions and interrupts to its normal workflow. This might be as simple as unplugging a network connection or cutting power to see how the system reacts or recovers from such interrupts. Manual intrusion or hacking may also be done, especially if the system is being tested for network security and vulnerability. In some testing environments, the system being tested is run concurrently with other systems, ensuring that there is a scarcity of resources. This is a way to find out if the system can cope with such problems.