How can I use a multimeter to replace electrical testers, etc.?
I have a multimeter and I don't want to spend more money on other electrical test devices.


While, I understand your thought process, keep in mind that multi-meters, when combined with house wiring are not nearly as safe to operate as devices designed to perform these tests.  You are paying not only for utility but also for safety (which is far more important).


  circuit tester


I guess you mean outlet tester specifically.


Set your Cat II or better rated multimeter to a high voltage AC range. If your meter has a Low-Z range intended for 120 V AC (or 230 V AC), use that.
Double check that you have the leads in the right sockets for voltage testing.
Measure the voltage


between ground and neutral
between ground and hot
between hot and neutral

Check that the results match what you expect (e.g. 0, 120, 120).



  GFCI outlet tester


You can't test this with just a multimeter. You need a load that will pass about 8mA at 120V (or >30mA at 230V for UK/EU readers) between hot and ground.

(Note, according to NEMA, a GFCI "test" button uses a 15kΩ resistor with a suitable voltage rating. This means the test current is nominally 8mA at 120V (or up to 9mA for a 10% tolerance resistor)

A typical multimeter has a 10MΩ impedance on its AC voltage ranges, so it passes less than 12 micro-Amps at 120V - too small to trip a GFCI. A "low-Z" range might use a 3kΩ impedance and pass 40mA at 120V - this is more than is needed for safely testing a GFCI. Note that around 10mA is the let-go threshold for humans and so currents above that can be problematic. 

Fabricating something that is safe for use with 120 V AC is going be difficult to do for less than the cost of a purpose built tool.