Assertions & Extractors

Overview

HTTP and FastHttp tasks accept assertions and extract blocks that run under Locust’s catch_response. Failed assertions mark the request as a Locust failure and surface in every report.

Assertions

`type`	Behaviour
`status_code`	`int(response.status_code) == int(value)`.
`contains`	`str(value) in response.text`.
`not_contains`	`str(value) not in response.text`.
`json_path`	Resolves `response.json()` along `path` (dot-separated; list indices supported) and compares to `value`.
`header`	`response.headers[name] == value`.

Example

{
  "method": "get",
  "request_url": "${var.base}/health",
  "assertions": [
    {"type": "status_code", "value": 200},
    {"type": "json_path", "path": "status", "value": "ok"},
    {"type": "header", "name": "X-Service", "value": "checkout"}
  ]
}

Extractors

`from`	Source
`json_path`	Same dotted path syntax as the `json_path` assertion.
`header`	`response.headers[name]`.
`status_code`	`response.status_code`.

Extracted values are written into the parameter resolver under the chosen var name; subsequent tasks reference them as ${var.NAME}.

{
  "method": "post",
  "request_url": "${var.base}/login",
  "json": {"email": "u@example.com", "password": "secret"},
  "extract": [
    {"var": "auth_token", "from": "json_path", "path": "data.token"},
    {"var": "request_id", "from": "header",    "name": "X-Request-Id"}
  ]
}