6. Thread the scenario state through the steps

Date: 2014-08-08, amended 2026-08-30

Status

Accepted

Context

Steps need to share data: the product a When creates is the one a Then checks. Cucumber implementations use a world object, often filled by dependency injection.

Decision

Each step receives, as first argument, what the previous step returned -- like a chain of Ring handlers. The first step receives {}, or the feature's :default-scenario-state.

Amended 2026-08-30: a step returning nil or a boolean keeps the state it was given. That is what an assertion (is) or a side effect (doseq, println) returns, and a defthen that forgot its trailing state silently replaced the state with true.

Consequences

• No world object, no dependency injection, no mutable state: a step is a plain function of its input.
• A step cannot set the state to nil or false.