mocks/

Mock contracts live as YAML files under mocks/, conventionally named after the action with slashes replaced by dashes: actions-checkout-v4.yml.

uses: actions/setup-node@v4
description: Synthesizes setup-node outputs without touching the network
inputs:
  node-version:
    required: false
    default: "20"
  # Scalar shorthand is accepted: <name>: <value>
  cache: npm
outputs:
  node-version: "20.11.1"
  cache-hit: "true"
durationMs: 350

Key	Description
uses	The action reference this contract matches. Exactly one of uses or stepId is required.
stepId	Match a specific step id instead of an action reference.
description	Free-text note shown in tooling.
inputs	Expected inputs. Each entry is a declaration (description, required, default), a scalar shorthand treated as the default, or a bare name.
outputs	Outputs the mocked step returns. Values are coerced to strings.
durationMs	Simulated duration for the step.

At run time a mocked step validates required inputs against the action’s real action.yml and returns the declared outputs, so ${{ steps.<id>.outputs.* }} expressions keep working downstream.

Generate contracts with overwire seed-mocks, including --from-run to capture outputs a real run produced, or overwire resolve --contract for a single action.