export interface JsonInit extends RequestInit {
    /**
     * Serialized as the request body, with `content-type: application/json` set
     * unless `headers` already carries one. Covers every verb, so there is no
     * `post()`/`put()`/`patch()` triple here. Takes precedence over `body`.
     */
    readonly json?: unknown;
}
export interface JsonResponse<T> {
    readonly status: number;
    readonly headers: Headers;
    readonly body: T;
}
/**
 * `fetch` against one base URL, plus the JSON round-trip every suite otherwise
 * rewrites. Deliberately not an assertion DSL: it returns values that `expect`
 * already reads well, so failures point at the assertion rather than at a matcher
 * this package would have to define.
 *
 * `createTestServer` returns one of these already bound to the server it started;
 * this is here for an app booted some other way.
 */
export declare class TestClient {
    /** The server's base URL, as `listen()` returned it. */
    readonly url: string;
    constructor(url: string);
    /** The raw `Response` - for bytes, HTML, or asserting on a header. */
    request(path?: string, init?: JsonInit): Promise<Response>;
    /** Status, headers and parsed body in one await, which is the common assertion. */
    json<T = unknown>(path?: string, init?: JsonInit): Promise<JsonResponse<T>>;
}
/** `new TestClient(url)`. */
export declare const testClient: (url: string) => TestClient;