Lesson 5: C# setup and .NET foundations: Testing focus

Concept Explanation

"C# setup and .NET foundations: Testing focus" introduces the habit of checking small pieces of code early instead of assuming they work. In this lesson, you will write a tiny method, call it with a few clear inputs, and confirm that the result matches what you expected. The goal is not to learn a full testing framework yet, but to understand what a useful test looks like: one input, one expectation, and a result you can verify quickly. By the end, you should be comfortable turning a simple C# example into something easier to trust, change, and debug.

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

• Write down the expected result before you run each check.
• Test one normal case and one edge case, such as adding zero or a negative number.
• Keep the method small so the output is easy to verify by eye.
• Refactor names only after the behavior is already correct.

Step-by-step Guide

1. Run the example once and confirm both checks print True.
2. Change one input pair and predict the result before running the code again.
3. Add one more check that uses zero as one of the values.
4. Rename the method parameters if a clearer name helps readability.
5. Finish with a short note about why small checks make later debugging easier.

Practice Exercises

• Create a Subtract method and verify it with two quick checks.
• Add a Multiply method and test it with a positive case and a zero case.
• Rewrite the example so the method and checks are still simple but more descriptive.

Coding Challenges

• Group your checks so someone new to the file can tell what behavior is being verified.
• Compare checking output with Console.WriteLine versus returning values and explain which is easier to test.

Mini Practice Tasks

• Rename one variable or parameter for clarity.
• Add one extra verification line and run it.
• Write one sentence describing what this test code is proving.