Lesson 5: Java setup and execution model: Testing focus

Concept Explanation

Testing focus in this lesson means learning how to trust what your program prints instead of just hoping it works. At this stage in Java, the goal is simple: write a small piece of logic, run it with a few known inputs, and check that the result matches your expectation every time. You are not building a full test suite yet. You are building the habit of verifying behavior after each change. That habit matters in every Java project, whether you are writing a tiny console tool or a larger backend service. By the end of the lesson, you should be comfortable making a change, rerunning the program, and confirming both a normal case and a boundary case before moving on.

Where to Put the Code

1. Define color and position variables at the top.
2. Create shape drawing or placement logic in the middle.
3. Render output (print, canvas, SVG, or styled block) at the end.

Command Reference

• Run the program once and record the output for all three checks.
• Change one input value, then rerun the file and confirm which line changes.
• Add one extra check for an edge case such as 0 hours and 59 minutes.
• Write down one reason testing early saves time while learning Java.

Step-by-step Guide

1. Read the method and explain in one sentence what result it returns.
2. Compile and run the starter code before changing anything.
3. Confirm that each check label matches the correct output line.
4. Add one more test case of your own and run the file again.
5. Note which case felt easiest to verify and which one required more attention.

Practice Exercises

• Create a second helper method that converts only hours into minutes and test it.
• Replace one passing check with a failing value so you can see the error message format.
• Build a similar mini program that tests a method for converting days into hours.

Coding Challenges

• Refactor the checking logic so the output stays readable even when you add five more cases.
• Design a small example where a wrong expected value makes the program look broken even though the method is correct.

Mini Practice Tasks

• Rename one method so its purpose is clearer at first glance.
• Add one short comment above the method being tested.
• Write one line describing the difference between running code and verifying code.