{
  "name": "test subject",               // A string that names the test 
  "expects": ["identity,en"],           // A list of normalised variant-ids that we expect to match
  "stored_responses": [                 // A list of HTTP responses in the cache.
    {                                   // Currently only the first is used.
      "variants": [                     // Header field name; must be lowercase
        ["Accept-Encoding", "gzip"],    // [field-name, field-value] tuples; any case for names
        ["Accept-Language", "en", "fr"]
      ],
      "variant-key": ["gzip,en"]        // Most responses will need both variants and variant-key
    }
  ],
  "request": {                          // The incoming request
    "accept-encoding": ["br"],          // Header field-names, field-values. Names need to be lc
    "accept-language": ["de"]           // Values are lists
  }
}