Hooks Reference

Schema-Level Hooks

Hook	Signature	When / Why
before_load_schema	(context, raw_schema: dict) -> None	Modify the raw schema before parsing (e.g., inject const values, patch syntax).
after_load_schema	(context, schema: BaseSchema) -> None	Inspect or mutate the loaded schema object (e.g., add links, override formats).
before_process_path	(context, path: str, methods: dict) -> None	Tweak a specific endpoint’s definition (e.g., set parameter defaults from your DB).
before_init_operation	(context, operation: APIOperation) -> None	Adjust an APIOperation before building strategies (e.g., restrict enum choices, set defaults).
before_add_examples	(context, examples: list[Case]) -> None	Append explicit Case instances before the examples phase.

Data-Generation Hooks

Request-Lifecycle Hooks

Mutate or inspect the test case and HTTP request flow.

Hook	Signature	When / Why
before_call	(context, case: Case) -> None	Right before sending the HTTP request; modify case (e.g., add headers, tweak query).
process_call_kwargs	(context, case: Case, kwargs: dict) -> dict	Alter keyword args to case.call(**kwargs) (e.g., disable redirects, set timeouts).
after_call	(context, case: Case, response: Response) -> None	Immediately after a successful call; inspect or mutate response before built-in checks.

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Conditional Application

Apply hooks only to matching API operations:

@schemathesis.hook.apply_to(path_regex=r"^/users/")  
                  .skip_for(method="POST", tag="admin")
def map_headers(context, headers):
    headers = headers or {}
    headers["X-User-Test"] = "true"
    return headers

• apply_to(...): target operations matching all given conditions (AND logic).
• skip_for(...): exclude operations matching any given conditions (OR logic).

Supported filters: path, path_regex, method, name, tag, operation_id (accepts string, list, or <field>_regex).