Test-Driven Development (TDD) for Laravel

Overview

Write the test first. Watch it fail. Write minimal code to pass.

Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.

Violating the letter of the rules is violating the spirit of the rules.

When to Use

Always:

New features
Bug fixes
Refactoring
Behavior changes

Exceptions (ask your human partner):

Throwaway prototypes
Generated code (migrations, factories)
Configuration files

Thinking "skip TDD just this once"? Stop. That's rationalization.

The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Write code before the test? Delete it. Start over.

No exceptions:

Don't keep it as "reference"
Don't "adapt" it while writing tests
Don't look at it
Delete means delete

Implement fresh from tests. Period.

Red-Green-Refactor

RED - Write Failing Test

Write one minimal test showing what should happen.

Good:

php

test('retries failed operations 3 times', function () {
    $attempts = 0;

    $operation = function () use (&$attempts) {
        $attempts++;
        if ($attempts < 3) {
            throw new Exception('fail');
        }
        return 'success';
    };

    $result = retryOperation($operation);

    expect($result)->toBe('success');
    expect($attempts)->toBe(3);
});

Clear name, tests real behavior, one thing

Bad:

php

test('retry works', function () {
    $mock = Mockery::mock(SomeService::class);
    $mock->shouldReceive('call')
        ->times(3)
        ->andThrow(new Exception(), new Exception())
        ->andReturn('success');

    retryOperation(fn () => $mock->call());

    // Only verifies mock was called, not actual behavior
});

Vague name, tests mock not code

Requirements:

One behavior
Clear name
Real code (no mocks unless unavoidable)

Verify RED - Watch It Fail

MANDATORY. Never skip.

bash

php artisan test --filter="retries failed operations"

Confirm:

Test fails (not errors)
Failure message is expected
Fails because feature missing (not typos)

Test passes? You're testing existing behavior. Fix test.

Test errors? Fix error, re-run until it fails correctly.

GREEN - Minimal Code

Write simplest code to pass the test.

Good:

php

function retryOperation(callable $fn, int $maxRetries = 3): mixed
{
    for ($i = 0; $i < $maxRetries; $i++) {
        try {
            return $fn();
        } catch (Exception $e) {
            if ($i === $maxRetries - 1) {
                throw $e;
            }
        }
    }
}

Just enough to pass

Bad:

php

function retryOperation(
    callable $fn,
    int $maxRetries = 3,
    string $backoff = 'exponential',
    ?callable $onRetry = null,
    ?LoggerInterface $logger = null,
): mixed {
    // YAGNI - You Aren't Gonna Need It
}

Over-engineered

Don't add features, refactor other code, or "improve" beyond the test.

Verify GREEN - Watch It Pass

MANDATORY.

bash

php artisan test --filter="retries failed operations"

Confirm:

Test passes
Other tests still pass
Output pristine (no errors, warnings, deprecations)

Test fails? Fix code, not test.

Other tests fail? Fix now.

REFACTOR - Clean Up

After green only:

Remove duplication
Improve names
Extract to Actions, Services, or helpers

Keep tests green. Don't add behavior.

Repeat

Next failing test for next feature.

Good Tests

Quality	Good	Bad
Minimal	One thing. "and" in name? Split it.	`test('validates email and domain and whitespace')`
Clear	Name describes behavior	`test('test1')`
Shows intent	Demonstrates desired API	Obscures what code should do

Why Order Matters

"I'll write tests after to verify it works"

Tests written after code pass immediately. Passing immediately proves nothing:

Might test wrong thing
Might test implementation, not behavior
Might miss edge cases you forgot
You never saw it catch the bug

Test-first forces you to see the test fail, proving it actually tests something.

"I already manually tested all the edge cases"

Manual testing is ad-hoc. You think you tested everything but:

No record of what you tested
Can't re-run when code changes
Easy to forget cases under pressure
"It worked when I tried it" ≠ comprehensive

Automated tests are systematic. They run the same way every time.

"Deleting X hours of work is wasteful"

Sunk cost fallacy. The time is already gone. Your choice now:

Delete and rewrite with TDD (X more hours, high confidence)
Keep it and add tests after (30 min, low confidence, likely bugs)

The "waste" is keeping code you can't trust. Working code without real tests is technical debt.

"TDD is dogmatic, being pragmatic means adapting"

TDD IS pragmatic:

Finds bugs before commit (faster than debugging after)
Prevents regressions (tests catch breaks immediately)
Documents behavior (tests show how to use code)
Enables refactoring (change freely, tests catch breaks)

"Pragmatic" shortcuts = debugging in production = slower.

"Tests after achieve the same goals - it's spirit not ritual"

No. Tests-after answer "What does this do?" Tests-first answer "What should this do?"

Tests-after are biased by your implementation. You test what you built, not what's required. You verify remembered edge cases, not discovered ones.

Tests-first force edge case discovery before implementing. Tests-after verify you remembered everything (you didn't).

30 minutes of tests after ≠ TDD. You get coverage, lose proof tests work.

Common Rationalizations

Excuse	Reality
"Too simple to test"	Simple code breaks. Test takes 30 seconds.
"I'll test after"	Tests passing immediately prove nothing.
"Tests after achieve same goals"	Tests-after = "what does this do?" Tests-first = "what should this do?"
"Already manually tested"	Ad-hoc ≠ systematic. No record, can't re-run.
"Deleting X hours is wasteful"	Sunk cost fallacy. Keeping unverified code is technical debt.
"Keep as reference, write tests first"	You'll adapt it. That's testing after. Delete means delete.
"Need to explore first"	Fine. Throw away exploration, start with TDD.
"Test hard = design unclear"	Listen to test. Hard to test = hard to use.
"TDD will slow me down"	TDD faster than debugging. Pragmatic = test-first.
"Manual test faster"	Manual doesn't prove edge cases. You'll re-test every change.
"Existing code has no tests"	You're improving it. Add tests for existing code.

Red Flags - STOP and Start Over

Code before test
Test after implementation
Test passes immediately
Can't explain why test failed
Tests added "later"
Rationalizing "just this once"
"I already manually tested it"
"Tests after achieve the same purpose"
"It's about spirit not ritual"
"Keep as reference" or "adapt existing code"
"Already spent X hours, deleting is wasteful"
"TDD is dogmatic, I'm being pragmatic"
"This is different because..."

All of these mean: Delete code. Start over with TDD.

Laravel-Specific Examples

Example: Bug Fix with Form Request

Bug: Empty email accepted

RED

php

test('rejects empty email', function () {
    $response = $this->postJson('/api/users', [
        'email' => '',
        'name' => 'Test User',
    ]);

    $response->assertStatus(422)
        ->assertJsonValidationErrors(['email']);
});

Verify RED

bash

$ php artisan test --filter="rejects empty email"
FAIL: Expected status 422, got 200

GREEN

php

// app/Http/Requests/StoreUserRequest.php
class StoreUserRequest extends FormRequest
{
    public function rules(): array
    {
        return [
            'email' => ['required', 'email'],
            'name' => ['required', 'string'],
        ];
    }
}

Verify GREEN

bash

$ php artisan test --filter="rejects empty email"
PASS

Example: Action Class

RED

php

test('calculate order total includes tax', function () {
    $order = Order::factory()->create([
        'subtotal' => 10000, // $100.00 in cents
    ]);

    $action = new CalculateOrderTotalAction();
    $result = $action->execute($order, taxRate: 0.08);

    expect($result->total)->toBe(10800);
    expect($result->tax)->toBe(800);
});

Verify RED

bash

$ php artisan test --filter="calculate order total"
FAIL: Class CalculateOrderTotalAction not found

GREEN

php

// app/Actions/CalculateOrderTotalAction.php
class CalculateOrderTotalAction
{
    public function execute(Order $order, float $taxRate): OrderTotal
    {
        $tax = (int) round($order->subtotal * $taxRate);

        return new OrderTotal(
            subtotal: $order->subtotal,
            tax: $tax,
            total: $order->subtotal + $tax,
        );
    }
}

Verify GREEN

bash

$ php artisan test --filter="calculate order total"
PASS

Example: Policy/Gate Authorization

RED

php

test('users can only view their own orders', function () {
    $user = User::factory()->create();
    $otherUser = User::factory()->create();
    $order = Order::factory()->for($otherUser)->create();

    $this->actingAs($user);

    expect($user->can('view', $order))->toBeFalse();
});

test('users can view their own orders', function () {
    $user = User::factory()->create();
    $order = Order::factory()->for($user)->create();

    $this->actingAs($user);

    expect($user->can('view', $order))->toBeTrue();
});

GREEN

php

// app/Policies/OrderPolicy.php
class OrderPolicy
{
    public function view(User $user, Order $order): bool
    {
        return $user->id === $order->user_id;
    }
}

Example: Eloquent Scope

RED

php

test('active scope returns only active users', function () {
    User::factory()->count(3)->create(['active' => true]);
    User::factory()->count(2)->create(['active' => false]);

    $activeUsers = User::active()->get();

    expect($activeUsers)->toHaveCount(3);
    expect($activeUsers->pluck('active')->unique()->all())->toBe([true]);
});

GREEN

php

// app/Models/User.php
public function scopeActive(Builder $query): Builder
{
    return $query->where('active', true);
}

Example: Job/Queue

RED

php

use Illuminate\Support\Facades\Queue;

test('order completion dispatches notification job', function () {
    Queue::fake();

    $order = Order::factory()->create();
    $action = new CompleteOrderAction();

    $action->execute($order);

    Queue::assertPushed(SendOrderCompletionNotification::class, function ($job) use ($order) {
        return $job->order->id === $order->id;
    });
});

GREEN

php

class CompleteOrderAction
{
    public function execute(Order $order): void
    {
        $order->update(['status' => 'completed']);

        SendOrderCompletionNotification::dispatch($order);
    }
}

Example: Event Listener

RED

php

use Illuminate\Support\Facades\Event;

test('user registration fires UserRegistered event', function () {
    Event::fake([UserRegistered::class]);

    $action = new RegisterUserAction();
    $user = $action->execute([
        'email' => 'test@example.com',
        'password' => 'password',
    ]);

    Event::assertDispatched(UserRegistered::class, function ($event) use ($user) {
        return $event->user->id === $user->id;
    });
});

GREEN

php

class RegisterUserAction
{
    public function execute(array $data): User
    {
        $user = User::create([
            'email' => $data['email'],
            'password' => Hash::make($data['password']),
        ]);

        event(new UserRegistered($user));

        return $user;
    }
}

Pest-Specific Features

Use

describe

for Grouping Related Tests

php

describe('OrderPolicy', function () {
    test('owners can view their orders', function () {
        // ...
    });

    test('owners can cancel pending orders', function () {
        // ...
    });

    test('owners cannot cancel shipped orders', function () {
        // ...
    });
});

Use

beforeEach

for Common Setup

php

beforeEach(function () {
    $this->user = User::factory()->create();
    $this->actingAs($this->user);
});

test('can create order', function () {
    // $this->user is available
});

Use Datasets for Parameterized Tests

php

dataset('invalid_emails', [
    'empty string' => [''],
    'missing @' => ['invalidemail.com'],
    'missing domain' => ['test@'],
    'spaces' => ['test @example.com'],
]);

test('rejects invalid email formats', function (string $email) {
    $response = $this->postJson('/api/users', [
        'email' => $email,
        'name' => 'Test',
    ]);

    $response->assertJsonValidationErrors(['email']);
})->with('invalid_emails');

Use Higher-Order Tests for Simple Cases

php

test('homepage loads successfully')
    ->get('/')
    ->assertOk();

test('guests cannot access dashboard')
    ->get('/dashboard')
    ->assertRedirect('/login');

Verification Checklist

Before marking work complete:

Every new Action/Service/Model method has a test
Watched each test fail before implementing
Each test failed for expected reason (feature missing, not typo)
Wrote minimal code to pass each test
All tests pass:
```
php artisan test
```
Output pristine (no errors, warnings, deprecations)
Tests use real code (fakes only for external services)
Edge cases and errors covered

Can't check all boxes? You skipped TDD. Start over.

Useful Commands

bash

# Run all tests
php artisan test

# Run specific test by name
php artisan test --filter="rejects empty email"

# Run specific test file
php artisan test tests/Feature/OrderTest.php

# Run tests in parallel
php artisan test --parallel

# Run with coverage
php artisan test --coverage

# Run and stop on first failure
php artisan test --stop-on-failure

# Run only dirty tests (changed files)
php artisan test --dirty

When Stuck

Problem	Solution
Don't know how to test	Write wished-for API. Write assertion first. Ask your human partner.
Test too complicated	Design too complicated. Simplify interface.
Must mock everything	Code too coupled. Use dependency injection.
Test setup huge	Use factories, traits, helpers. Still complex? Simplify design.
Database slow	Use `RefreshDatabase` or `LazilyRefreshDatabase` trait.

Debugging Integration

Bug found? Write failing test reproducing it. Follow TDD cycle. Test proves fix and prevents regression.

Never fix bugs without a test.

Final Rule

Production code → test exists and failed first
Otherwise → not TDD

No exceptions without your human partner's permission.

test-driven-development

NPX Install

SKILL.md Content

Test-Driven Development (TDD) for Laravel

Overview

When to Use

The Iron Law

Red-Green-Refactor

RED - Write Failing Test

Verify RED - Watch It Fail

GREEN - Minimal Code

Verify GREEN - Watch It Pass

REFACTOR - Clean Up

Repeat

Good Tests

Why Order Matters

Common Rationalizations

Red Flags - STOP and Start Over

Laravel-Specific Examples

Example: Bug Fix with Form Request

Example: Action Class

Example: Policy/Gate Authorization

Example: Eloquent Scope

Example: Job/Queue

Example: Event Listener

Pest-Specific Features

Use
`describe`
for Grouping Related Tests

Use
`beforeEach`
for Common Setup

Use Datasets for Parameterized Tests

Use Higher-Order Tests for Simple Cases

Verification Checklist

Useful Commands

When Stuck

Debugging Integration

Final Rule