Скачать или смотреть 🧪 Functional vs Non-Functional Testing (Explained for Real-World QA)

Every app needs two types of testing to survive in the real world: Functional Testing (does it work?) and Non-Functional Testing (does it perform well?).
Both are 🔐 essentials for smooth user experience.


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💡 WHAT IS FUNCTIONAL TESTING?

Functional Testing checks whether the app behaves exactly as expected.

It answers:
👉 “Is the feature doing the right thing?”

📌 We verify UI actions, workflows, validation rules, navigation, etc.


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🧠 Analogy

Like checking if every switch in your house turns ON the correct light.


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📍 Real Example — Login

You test:

Valid login → Goes to dashboard

Wrong password → Shows error

Forgot password → Works properly


Basically: All flows must behave correctly.


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🔎 Purpose

✔ Confirm the app meets requirements
✔ Validate functional behavior
✔ Ensure the user journey works


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🧭 Types of Functional Testing

🔹 1) Unit Testing

Tests a single piece (like login logic).
Done by developers.

🔹 2) Integration Testing

Tests combined pieces (login + dashboard flow).

🔹 3) System Testing

Tests whole application end-to-end.
Done by QA teams.

🔹 4) Acceptance Testing

Users/clients confirm everything meets their needs before go-live.


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🚀 WHAT IS NON-FUNCTIONAL TESTING?

Non-Functional Testing checks how well the app performs, not what it does.

It answers:
👉 “Is the app fast, secure, reliable?”


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🧠 Analogy

Having a car isn’t enough — it must be smooth, safe, fuel-efficient, and comfy.


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📍 Real Example — Performance

Simulate 1,000 users logging in simultaneously.
You measure:

Response time

Crash risk

Slowdowns



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🔎 Purpose

✔ Stability
✔ Reliability
✔ Security
✔ Fast performance


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🧭 Types of Non-Functional Testing

⚡ 1) Performance Testing

Checks speed, responsiveness.

🛡 2) Security Testing

Protects user data.

🎯 3) Usability Testing

Confirms the app is smooth and intuitive.

🌐 4) Compatibility Testing

Works across browsers/devices (Chrome, Firefox, iPhone, Samsung).

🔁 5) Reliability Testing

App works without failure, even under load.


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🤝 WHY DO WE NEED BOTH?

Functional Testing Non-Functional Testing

Checks what app does Checks how app performs
Finds functional bugs Finds performance/UX issues
Validates features Validates experience


📝 Bottom line:
Functional = Does the job
Non-Functional = Does the job WELL


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🧵 WHEN & WHO DOES WHAT?

🧪 Functional Testing

Starts early (during dev)

Developers + QA

Ends before release


🔐 Non-Functional Testing

Happens after functional passes

Done by performance/security specialists



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🏁 KEY TAKEAWAYS

✔ Functional = requirement-based testing
✔ Non-Functional = performance, experience, efficiency
✔ You can't release without BOTH
✔ Functional ensures correctness
✔ Non-Functional ensures quality


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🔥 TL;DR (Gen-Z style)

Functional → "Does it work?"
Non-Functional → "Is it 🔥 fast, secure, stable?"


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