Test Types and Levels

Test Types

Property	Value
Scope	Single function / class / module
Speed	Sub-millisecond
Dependencies	All replaced with mocks/stubs
Feedback	Immediate; drives TDD

Key rules: - One logical assertion per test - No I/O, no network, no database - Test behaviour, not internal state

Property	Value
Scope	Two or more components interacting
Speed	Milliseconds to seconds
Dependencies	Real or containerised (DB, cache, queue)
Feedback	Reveals wiring and contract issues

Key rules: - Isolate external third-party APIs with stubs - Use transactions or truncation for DB teardown - One integration concern per test suite

Protocol	Focus
REST	Status codes, schema (OpenAPI/JSON Schema), headers, pagination
GraphQL	Query shape, resolver errors, schema introspection
gRPC	Protobuf contract, status codes, streaming frames
WebSocket	Handshake, message ordering, reconnect behaviour

Common patterns: request builder + response validator + schema assertion.

Property	Value
Scope	Full user journey through deployed stack
Speed	Seconds to minutes
Dependencies	Real environment
Feedback	Confirms business flows work

Risks: flaky selectors, timing issues, environment coupling. Mitigation: stable locators, explicit waits, retry logic.

Side	Responsibility
Consumer	Defines expected API shape
Provider	Verifies it can satisfy the consumer contract

Tools: Pact (HTTP), Pact Broker, gRPC reflection + schema registry.

Consumer-driven contract tests prevent breaking changes across service boundaries.