this is what we use at Spiko: ```ts import { HttpApiClient, HttpClientResponse } from '@effect/platform'; import { Context, Effect } from 'effect'; type HttpClientTag = // eslint-disable-next-line @typescript-eslint/no-explicit-any | Context.Tag> // eslint-disable-next-line @typescript-eslint/no-explicit-any | Context.TagClassShape>; export type PartialHttpApiClient = Partial<{ [K in keyof Context.Tag.Service]: Partial[K]>; }>; type HttpApiClientMockDefaults = { [K in keyof Context.Tag.Service]: Context.Tag.Service[K]; }; export const mockClient = (defaults: HttpApiClientMockDefaults) => (mock: PartialHttpApiClient = {}): Context.Tag.Service => Object.entries(mock).reduce( (acc, [key, value]) => ({ ...acc, [key]: { ...defaults[key], ...value }, }), defaults as Context.Tag.Service ); export const mockHttpApiMethod = ( fn: (request: Req) => Effect.Effect ) => (request: Req): Effect.Effect => Effect.map(fn(request), (response) => request !== undefined && request.withResponse ? ([response, {} as HttpClientResponse.HttpClientResponse] as const) : response ) as Effect.Effect; ``` and then you can mock your client like this: ```ts const mockApiClient = mockClient({ group: { endpoint: mockHttpApiMethod(() => Effect.succeed({})), } }) ```