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Built-in checks

checks looks for two kinds of mistake that need no configuration to define: a body whose content type does not match what it holds, and, when you give it a configuration file, a required header that is missing.

wiretrail checkout.har checks

[content-type] api.shop.example /v1/track
  request JSON body without application/json content-type (3 entries)

[content-type] api.shop.example /v1/legacy/status
  JSON response served as text/html (1 entries)

[content-type] api.shop.example /v1/cart/items/{id}
  empty body with JSON content-type (1 entries)

Content-type checks

Finding What WireTrail saw
request JSON body without application/json content-type The request body starts with { or [ and the request's Content-Type does not contain json.
JSON response served as text/html The response body starts with { or [ and the response content type contains html.
empty body with JSON content-type A 200 response with a JSON content type and no body.

Each finding names the host and normalized path and counts the entries. On a capture that kept its bodies, these are real defects, and they matter: a server that gets JSON labelled as plain text may parse it differently, and a client that gets JSON labelled as HTML may refuse to read it.

If the capture was saved without response bodies (validate shows response bodies: 0%), the check for an empty body fires on every 200 response with a JSON content type. Ignore it for such a capture.

Required headers

A configuration file can name headers that every request to a host must carry:

required_headers:
  - host: "api.shop.example"
    headers: ["X-App-Version"]

wiretrail checkout.har checks --config config/wiretrail.yaml

[missing-header] api.shop.example /v1/track
  missing required header: X-App-Version (3 entries)

host is a glob. Header names ignore case. A finding appears for each header that a matching request lacks. Without a configuration file, checks runs only the content-type checks.

required_headers is for checks. The rules: list in the same file has a similar require_headers key, which belongs to rules and adds matchers by path, method and status.

JSON

wiretrail checkout.har checks --json | jq '.result.findings[0]'

{
  "rule": "content-type",
  "host": "api.shop.example",
  "norm_path": "/v1/track",
  "detail": "request JSON body without application/json content-type",
  "entry_ids": [
    "e000093",
    "e000094",
    "e000095"
  ]
}

Exit code

checks exits 1 when it reports any finding and 0 when it reports none.