Function stub

testing/unstable_stub.ts:152–283

(
  self: Self,
  property: keyof Self,
  descriptorOrFunction?:
    | ((this: Self, ...args: Args) => Return)
    | Omit<PropertyDescriptor, "configurable">,
)

    >;
  };
export function stub<Self, Args extends unknown[], Return>(
  self: Self,
  property: keyof Self,
  descriptorOrFunction?:
    | ((this: Self, ...args: Args) => Return)
    | Omit<PropertyDescriptor, "configurable">,
): Stub<Self, Args, Return> {
  if (
    self[property] !== undefined &&
    typeof self[property] !== "function" &&
    (descriptorOrFunction === undefined ||
      typeof descriptorOrFunction === "function")
  ) {
    throw new MockError("Cannot stub: property is not an instance method");
  }
  if (isSpy(self[property])) {
    throw new MockError("Cannot stub: already spying on instance method");
  }
  if (
    descriptorOrFunction !== undefined &&
    typeof descriptorOrFunction !== "function" &&
    descriptorOrFunction.get === undefined &&
    descriptorOrFunction.set === undefined
  ) {
    throw new MockError(
      "Cannot stub: neither setter nor getter is defined",
    );
  }

  const propertyDescriptor = Object.getOwnPropertyDescriptor(self, property);
  if (propertyDescriptor && !propertyDescriptor.configurable) {
    throw new MockError("Cannot stub: non-configurable instance method");
  }
  const fake =
    descriptorOrFunction && typeof descriptorOrFunction === "function"
      ? descriptorOrFunction
      : ((() => {}) as (this: Self, ...args: Args) => Return);

  const original = self[property] as unknown as (
    this: Self,
    ...args: Args
  ) => Return;
  const calls: SpyCall<Self, Args, Return>[] = [];
  let restored = false;
  const stub = function (this: Self, ...args: Args): Return {
    const call: SpyCall<Self, Args, Return> = { args };
    if (this) call.self = this;
    try {
      call.returned = fake.apply(this, args);
    } catch (error) {
      call.error = error as Error;
      calls.push(call);
      throw error;
    }
    calls.push(call);
    return call.returned;
  } as Stub<Self, Args, Return>;
  Object.defineProperties(stub, {