How do you replace services and Facades with Mocks in Laravel tests without breaking the system?

Short answer

Use built-in fakes such as Event::fake(), Queue::fake(), or Mail::fake(), and verify sends with Mail::assertSent().

Explanation

In tests, you do not want to send real email to a user or charge a real credit card. Laravel provides built-in fakes for core Facades; they intercept operations in memory and record what happened. This lets you verify that code attempted to send the required email with the right data without causing an actual external effect.

Code example

public function test_orders_trigger_mail(): void {
    Mail::fake();
    // Execute the purchase operation
    $this->postJson('/api/orders', $data);
    // Confirmation
    Mail::assertSent(OrderConfirmationMail::class);
}

Common mistakes

• Calling Mail::fake() after the code runs instead of before it.

Follow-up questions

• How do you test code that calls external APIs with Http::fake() and prevent real requests?
• How do multi-channel Notifications work in Laravel, and how do you test them with Notification::fake()?

Sources

• Laravel docs — Mocking