What is the difference between black-box and white-box testing?

Question

Accepted Answer

**Black-Box** — test without knowing internals. **White-Box** — test with knowledge of internals.

**Black-Box Testing:**
- No knowledge of code.
- Test inputs and outputs.
- User perspective.
- Functional testing.

```
Black-Box:
Input: username="john", password="123"
Output: login success or failure
(Don't know internal logic)
```

**White-Box Testing:**
- Knowledge of code.
- Test internal logic.
- Developer perspective.
- Structural testing.

```
White-Box:
Test all branches
Check code coverage
Know internal validation logic
(See internal structure)
```

**Key differences:**
- **Black-Box** — no code knowledge.
- **White-Box** — code knowledge.
- **Black-Box** — user perspective.
- **White-Box** — developer perspective.

Systems Analyst: What is the difference between black-box and white-box testing?