Checking Correctness with assert (Your First Step into Testing)

This lesson covers writing a simple test in Java, your first step toward the habit of verifying a program's correctness. It's for anyone searching "Java testing basics for beginners."

Learn the basic idea behind test code — checking whether a condition matches what you expect with an if statement. Automatically checking "does this function's result match what I expect" saves you from manually verifying it every time.

The example checks whether the result of add(2, 3) equals 5 with an if statement, printing "Test passed" if it matches and "Test failed" otherwise. You get a taste of the basic idea behind testing — verifying a result with code instead of eyeballing it.

A common early mistake is manually checking things every time and letting something slip through the cracks. Real work uses a dedicated testing framework (like JUnit), but the underlying idea is the same as what you learn here.

Keep in mind that an assertion like this is purely a debugging aid during development — it's not a substitute for real error handling in production.