Rules

Rules change traffic automatically: redirect a host, add a header, mock a body, force an error status.

• Request Mappings change requests before they reach the server.
• Response Mappings change responses before they reach your app.

Each rule has a checkbox in the list (or press ++space++) to turn it on and off without deleting it. Disabled rules stay in place, greyed out, and keep their order.

Free and Pro

The free edition runs up to three active rules at a time. Pro removes the limit.

Editing a rule

The editor has three modes that stay in sync:

• Visual — a form with conditions on one side and modifiers on the other.
• YAML and JSON — full source with completion, inline validation and quick documentation (uses the IDE's bundled JSON/YAML support).

Invalid drafts are kept, and errors point to the exact field (conditions.any[0].all[1] ...) or YAML line and column. Click Save Changes to apply.

How matching works

conditions:
  any:          # OR: the rule matches when any block matches
    - all:      # AND: every condition in the block must match
        - ...

Condition type	Checks
url	target: host, path or wholeUrl
query	A query parameter
header	A request or response header
body	A request or response body
status	The response status code (response rules)
all	Every response

Operators: equals and contains compare literal text, glob matches the whole value (* any text, ? one character), regex searches the value.

Modifiers run top to bottom, by category: URL → Headers → Body → Query for requests, Headers → Body → Status for responses.

Examples

Mock a server error

name: Login returns 500
conditions:
  any:
    - all:
        - type: url
          target: path
          operator: equals
          value: /api/login
modifiers:
  status:
    - action: set
      value: "500"
  body:
    - action: set
      value: '{"error": "server_down"}'

Send the app to staging

name: Use staging API
conditions:
  any:
    - all:
        - type: url
          target: host
          operator: equals
          value: api.example.com
modifiers:
  url:
    - action: setHost
      value: staging.example.com
      updateHostHeader: true

Add a debug header to every response

name: Debug header
conditions:
  any:
    - all:
        - type: all
modifiers:
  headers:
    - action: add
      name: X-Debug
      value: neocatcher

Modifier reference

Rules	Category	Actions
Request	url	setHost, setPath, setUrl, replaceHost, replacePath
Both	headers	add (keep existing), update (replace all with this name), remove
Both	body	set (whole body), replace (every occurrence of literal text)
Request	query	Change query parameters
Response	status	set (a code from 100 to 599, quoted)

The editor's completion lists every field with its documentation, so you rarely need this table.