To test whether a magnetron is good or bad, you can perform the following steps:

1. Safety Precautions: Before starting any test, ensure you unplug the magnetron from its power source. Magnetrons can be dangerous when powered on.

2. Visual Inspection: Examine the magnetron for any apparent physical damage such as cracks, burn marks, or loose connections. If any damage is detected, the magnetron is likely bad and needs replacement.

3. Continuity Test: To check the filament integrity, set a multimeter to the resistance (ohms) mode. Touch the multimeter probes to the terminals of the magnetron filament. A good magnetron will show continuity, meaning it should register a low resistance value. If the resistance is abnormally high or there is no continuity, the magnetron is bad.

4. Electrical Load Test: Using a multimeter, set to the resistance mode or use an ohmmeter, check the continuity between the magnetron's power terminals (taking into account the internal connections of the magnetron). This test helps to determine if the magnetron is shorted or open internally. Any abnormal readings indicate a bad magnetron.

5. Power Output Test: This test requires specialized equipment, known as a microwave power meter. Connect the magnetron to the power meter and observe the power output when it is activated. A good magnetron should produce the expected power output based on its specifications. If the power output is significantly lower than expected or if there is no output at all, the magnetron may be faulty.

Note: It's important to consult the manufacturer's documentation or seek professional assistance when performing these tests as magnetrons are sensitive and must be handled properly to ensure safety.

Remember, working with microwaves can be dangerous, so always prioritize safety and take the necessary precautions while conducting tests.