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

testing types
black-box
white-box
gray-box

Your answer

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Model answer

Black-box: test without knowledge of internal code, focus on inputs and outputs (functional testing, user perspective). White-box: test with full knowledge of code - focus on logic paths, branches, and internal state (unit testing, code review). Gray-box: partial knowledge - you understand the architecture and data flow but test through external interfaces (API testing with knowledge of the database schema). Most QA work is gray-box - you understand the system architecture but test through the UI or API rather than directly testing internal functions.

What interviewers listen for

Risk-based prioritisation
You can defend skipping coverage on a path because the risk maths supports it.
Test design fluency
You apply equivalence partitioning and decision tables to concrete inputs in real time.
Metric judgment
You distinguish between metrics that drive learning and metrics that drive theatre.
Strategy under constraint
You can produce a defensible plan when the team has half the time and twice the scope.

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