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Previously, you've used breakpoints to fix bugs, but now you're going to use unit testing to avoid

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bugs in this lesson, you're going to understand the importance of unit testing.

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Manual testing means running your code.

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The output determines if you have a bug.

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But the output doesn't tell you where the bug is.

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For example, I assume you've written a lot of code, then you run your application and the output determines

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you have a bug.

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OK, where's the bug?

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Now you have to inspect every single line of code to find your bug.

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This is terrible.

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Unit testing helps you avoid bugs.

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Unit testing means every small unit of your application has a test.

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As soon as you make a mistake, one of your tests is going to fail, the failing test tells you where

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you made a mistake.

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For example, as you're writing code, you make a mistake.

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The test for that unit of code fails immediately, the failing test tells you to fix your mistake.

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Once you fix it, the test passes.

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If every test passes, then, you know, your application doesn't have any bugs and you can continue

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coding with peace of mind.

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So what is the importance of unit testing?

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What if I don't unit test, you're going to hesitate to add code from fear of getting bugs.

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You're always going to be scared that one day your OP is going to break.

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But what if you do unit test, in that case, you'll never get bugs.

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Your code is always going to be polished.

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Unit testing helps you avoid bugs, every small unit in your application should have a test if you make

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a mistake, the test for that unit fails when you fix your mistake, the test for that unit passes.

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If every test passes, then your application doesn't have any bugs.