WEBVTT

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Debugging, testing, and refining OOP projects.

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In this video, we will learn to identify and fix bugs in OOP code.

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Use UnitTest to check if a class works correctly.

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Refine code to follow best practices and run smoothly.

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Let's start by learning how to find and fix bugs.

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First, we'll write a buggy code on purpose.

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Here, we have a simple bank account class with a withdrawal method.

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Now, if we try to take out more money than we have, it should block the withdrawal.

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But watch what happens when we run the program.

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The balance goes negative.

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That's the bug.

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Our code says insufficient funds, but still subtracts the money.

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So now we know exactly where the problem is.

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Debugging the code.

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To fix the bug, we add a condition.

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If the amount is greater than the balance, we stop right there and return false.

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This way, no money is removed when the withdrawal is invalid.

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Let's run it again.

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This time, when we try to take out more than we have, the program says insufficient funds.

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But the balance stays the same.

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And when we withdraw a valid amount, it works perfectly.

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The bug is gone.

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Testing the code.

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A unit test is like a checklist that makes sure our class works correctly.

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We test deposits, valid withdrawals, and invalid ones.

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When all tests pass, the program shows OK, which means our code is reliable.

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Refining the code.

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First, we change the balance variable to underscore balance and make it private.

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Then, we add a property so balance becomes read-only.

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We can check it, but not change it directly.

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Next, we improve the withdrawal method.

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We add checks so if the amount is zero, negative, or more than the balance,

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the program prints an error and stops.

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Only valid withdrawals are allowed.

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Finally, when we run it, the account starts with 100.

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A withdrawal of 150 is blocked with an error, but withdrawing 80 works fine.

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The final balance is updated correctly.

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Debugging helps us find and fix mistakes.

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Testing makes sure the code works and refining improves quality.

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Together, they turn an OOP project into a clean and reliable program.