How do I show that a singular word is louder than any other in a sentence when writing it?

I know that when a word is capitalized it expresses yelling.

What about text showing someone is talking and emphasizing a particular word, but he clearly isn't yelling the word out?

How is a "non-yelling" emphasis shown in text?

From: https://en.wikipedia.org/wiki/Stress_(linguistics)#Prosodic_stress

I didn't take the test yesterday. (Somebody else did.)

I didn't take the test yesterday. (I did not take it.)

I didn't take the test yesterday. (I did something else with it.)

I didn't take the test yesterday. (I took a different one.)

I didn't take the test yesterday. (I took something else.)

I didn't take the test yesterday. (I took it some other day.)

As in the examples above, stress is normally transcribed as italics in printed text or underlining in handwriting.