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Mimicker

Dynamic Responses

mimickerhq/mimicker

Dynamic Responses¶

response_func lets you compute the response at request time — inspect the request body, headers, path parameters, or query string and return any status code and body.

Basic usage¶

from mimicker.mimicker import mimicker, post

def greet(**kwargs):
    payload = kwargs.get("payload") or {}
    name = payload.get("name", "Guest")
    return 200, {"message": f"Hello, {name}!"}

mimicker(8080).routes(
    post("/greet").response_func(greet)
)

curl -X POST http://localhost:8080/greet -d '{"name": "World"}' -H 'Content-Type: application/json'
# {"message": "Hello, World!"}

curl -X POST http://localhost:8080/greet
# {"message": "Hello, Guest!"}

Available kwargs¶

Key	Type	Description
`payload`	`dict \\| None`	Parsed JSON request body (None if no body or not JSON)
`headers`	`dict[str, str]`	Lowercased request headers
`params`	`dict[str, str]`	Path parameter values (e.g. `{"id": "42"}`)
`query_params`	`dict[str, list[str]]`	Query string parameters (always lists)

Examples¶

Inspect request headers¶

def auth_check(**kwargs):
    token = kwargs["headers"].get("authorization", "")
    if token == "Bearer secret":
        return 200, {"authorized": True}
    return 401, {"error": "Unauthorized"}

mimicker(8080).routes(
    get("/protected").response_func(auth_check)
)

Echo path parameters¶

def echo_id(**kwargs):
    user_id = kwargs["params"]["id"]
    return 200, {"id": user_id, "fetched": True}

mimicker(8080).routes(
    get("/users/{id}").response_func(echo_id)
)

Use query parameters¶

def search(**kwargs):
    q = kwargs["query_params"].get("q", [""])[0]
    return 200, {"query": q, "results": []}

mimicker(8080).routes(
    get("/search").response_func(search)
)

Simulate conditional errors¶

def flaky_api(**kwargs):
    import random
    if random.random() < 0.3:
        return 503, {"error": "service unavailable"}
    return 200, {"data": "ok"}

mimicker(8080).routes(
    get("/api/data").response_func(flaky_api)
)

Combining with delay¶

response_func and .delay() can be combined on the same route:

mimicker(8080).routes(
    get("/slow").delay(0.5).response_func(my_func)
)

response_func vs sequence

Use response_func when the response depends on the request content. Use sequence (see Stubbing Guide) when the response depends on the call count — they serve different purposes.