To test a microwave for leaks, a possible method is to check for any interference in a home's Wi-Fi signal when the machine is turned on. A leaking microwave could also cause calls made using a cellphone to suddenly drop.
A microwave leak can also be tested using either a fluorescent or orange neon light bulbs. A fluorescent light bulb can be used to test for large microwave leaks as it causes the bulb to light up. Orange neon light bulbs are more sensitive and can detect smaller leaks. The FDA has also officially stated that some microwave testing products available in the market can be unreliable and inaccurate.