nw-tdd-methodology

Outside-in TDD in hexagonal architecture uses a double-loop approach to guide feature development from driving ports to driven ports. You define guiding acceptance tests first, implement top-level interfaces, and progressively replace mocks with real domain components.

Mock collaborators during outside-in TDD when defining boundaries between driving and driven ports. Apply test-doubles policies to isolate the system under test, then incrementally replace mocks with real domain implementations as the feature development progresses inward.

A walking skeleton in ATDD is a minimal end-to-end implementation that connects driving ports to driven ports. It establishes the port-to-port testing workflow within hexagonal architectures, providing a repeatable pattern for incremental TDD integration.

Structure driving ports as entry points for acceptance tests and driven ports as outbound dependencies to mock. This double-loop test-doubles policy maintains fast, reliable tests by isolating collaborators during outside-in TDD workflows.

Outside-in TDD suits project teams practicing ATDD and port-to-port testing within hexagonal architectures. It provides repeatable patterns for structuring interfaces and test doubles, applicable when refactoring toward clearer port boundaries.

Double-loop architecture in outside-in TDD separates acceptance-level guiding tests from unit-level implementation tests. This approach enables teams to define interfaces first, mock collaborators, and incrementally replace mocks with real domain components.