# Write unit tests, save time & lifes

Hey guys,

Unit testing or TDD (Test-driven development) has been a thing for years, hasn't it?

I'll quickly talk about this and share with you guys the experience.

### TDD

The practice of TDD is:

* You write test
    
* You write code
    
* You run test, test fails, you update the code until the test is passed
    

But honestly, in real life, we write the code first then write the test 🤣. It is acceptable as well.

### Unit Testing

You write a method/function, you write test for that function. That's basically how unit testing works.

Sample method:

```php
function createUser(string $fullName, int $age): User
{
    if ($age < 18) {
        throw new DomainException('User must be an Adult');
    }

    return User::create(['name' => $fullName, 'age' => $age]);
}
```

To write **good and reliable test cases,** you would need to cover all the cases:

* When the user's age is below 18
    
* When the user's age is above or equal to 18
    
* Data must be created successfully
    

Example:

```php
public function testCreateUserFailsDueToAgeBelow18()
{
    $this->expectException(DomainException::class);
    createUser('Seth Phat', 15);
}

public function testCreateUserSuccessfully()
{
    $user = createUser('Seth Phat', 18);

    $this->assertNotNull($user);
    $this->assertDatabaseHas('users', [
        'name' => 'Seth Phat',
        'age' => 18,
    ]);
}
```

Easy, right?

Write as many functions as possible. A minimal function would be super easy to write test.

### Pros of having unit testing

* More trust & confidence when releasing features.
    
* Refactoring would be fun and not scary at all, tests got your back.
    
    * When you refactor things and the test fails =&gt; you know something went wrong in the development phase.
        
* Same as refactoring: upgrading the framework, library, or language's version. You can list out the out-of-date/breaking changes and take needful actions from them.
    
    * Imagine upgrading the framework without tests, especially for major versions (eg Laravel 8.x to 9.x), it would cost a lot of time (and money) to do the regression test.
        

### Cons

* Yes yes I know, it takes time.
    

### Conclusion

Even if your project is a big product or an outsourcing one. Let's always write tests.

* Product:
    
    * Cover things as much as you can
        
    * Provide as many reliable tests as you can
        
* Outsourcing:
    
    * Integration test to test a big flow.
        
    * or E2E test, to test the important features.
        

Cheers!