Unit and Integration Testing

This topic covers the lower levels of the test pyramid. You write isolated unit tests following the Arrange-Act-Assert pattern, use test doubles (mocks and stubs) to isolate dependencies, and choose integration strategies to combine modules while localising failures.

Relation 1 —

Write this relation with symbols exactly as in Kaner Testing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 2 —

Write this relation with symbols exactly as in Kaner Testing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 3 —

Write this relation with symbols exactly as in Kaner Testing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Unit tests pin down a single module’s behaviour, and isolation is what makes them fast and precise — dependencies are replaced by test doubles so a failure points to the unit under test, not its collaborators. A stub feeds the unit predetermined inputs, while a mock additionally checks that the unit called its collaborators correctly. Integration testing then verifies the wiring between modules, where mismatched assumptions about interfaces surface; the strategy (top-down using stubs for lower modules, bottom-up using drivers for upper ones, or sandwich combining both) trades off how early different parts are exercised. Coverage measures how much code the tests execute, a necessary but not sufficient indicator of quality.

State assumptions explicitly before using any relation for unit and integration testing — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.

Wrong assumptions invalidate the entire solution even when the formula is correct. In Software Testing viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

1. Read the question and list given data with SI units (common in Software Testing papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to unit and integration testing.
4. Use equation 1: .
5. Use equation 2: .
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

Unit and Integration Testing appears in QA teams and CI pipelines. In Indian it software curricula this topic is tested because it connects theory to verification and validation.

GATE and semester exams often combine unit and integration testing with earlier units — revise prerequisites before attempting mixed problems.

Industry interview panels sometimes ask: "Where did you use unit and integration testing?" — answer with a lab, mini-project, or plant visit example if possible.

Students confuse mocks (verify interactions) with stubs (provide data), write unit tests that actually hit real dependencies (making them integration tests), and treat 100% coverage as proof of correctness. Forgetting that coverage measures execution, not assertion quality, is common.

Before attempting unit and integration testing problems, confirm you can:

1. AAA pattern: Arrange, Act, Assert
2. A mock verifies interaction; a stub returns canned data
3. Integration testing exposes interface mismatches

Revise the solved examples in Kaner Testing — Standard reference and one previous-year GATE or university paper for this unit.