Self-testing code is software that incorporates built-in tests (see test-first development).
[1][2] In Java, to execute a unit test from the command line, a class can have methods like the following.
To invoke a full system test, a class can incorporate a method call.
In addition, Java has some Jupiter API libraries for self-testing code.
assert can be used in various ways such as assert equals, which checks if the given variable is equal to the value given.