How can I know if an IR LED (emitter) is working, other than using a smartphone camera?

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I bought a lot of 5 mm, 940 nm IR LEDs like the picture below. I want to know if they are working or not. I tried the smartphone camera method, but I could not see the light. I have tested multiple of them, and I could not see the light with any of them, so I am not sure if the test itself is working or not.

I used a breadboard power supply and connected the LED like this:

5 V -> IR LED -> 270 ohm resistor -> ground

Am I supposed to see the light with the camera? Should I use a different resistor?

Is there a way to know if the IR LED is working without a camera, but with a multimeter? I have a cheap XL830L multimeter. With a regular LED (red, yellow), if I set the multimeter to 2 kilohm or 200 ohm, I could see the LED lighting, but the displayed value is 1 (error). If I do the same thing with the IR LED, of course the value is still 1, and I cannot see the light with the camera.