Testing and Debugging

Testing and debugging are essential parts of programming.

They show:

whether a program behaves as expected
whether the logic is correct
whether the programmer understands their own code

A program that “runs” is not automatically correct.

What Is Testing?

Testing is the process of checking program behaviour.

Testing asks questions such as:

Does the program give the correct output?
Does it handle unexpected input?
Does it behave correctly in all cases?

Testing should happen:

while the program is being built
after changes are made
before submission

Types of Testing

Common types of testing include:

normal case testing (expected input)
edge case testing (unusual but valid input)
error testing (invalid input)

Good testing shows intentional thinking, not guesswork.

What Is Debugging?

Debugging is the process of finding and fixing errors.

Errors may include:

syntax errors (the program won’t run)
logic errors (the program runs but behaves incorrectly)
runtime errors (the program crashes while running)

Debugging requires patience and careful reasoning.

The Debugging Process

Debugging usually involves:

identifying what is wrong
locating where the problem occurs
checking assumptions
making a small change
testing again

Figure 6 — Testing and debugging cycle

Debugging is rarely solved in one step.

Why Errors Are Useful

Errors:

reveal misunderstandings
highlight gaps in logic
help improve program structure

Making mistakes is normal.
Ignoring them is risky.