Function functionSpy

testing/mock.ts:408–451

Wraps a function with a Spy.

(func?: (this: Self, ...args: Args) => Return)

/** Wraps a function with a Spy. */
function functionSpy<
  Self,
  Args extends unknown[],
  Return,
>(func?: (this: Self, ...args: Args) => Return): Spy<Self, Args, Return> {
  const original = func ?? (() => {}) as (this: Self, ...args: Args) => Return;
  const calls: SpyCall<Self, Args, Return>[] = [];
  const spy = function (this: Self, ...args: Args): Return {
    const call: SpyCall<Self, Args, Return> = { args };
    if (this) call.self = this;
    try {
      call.returned = original.apply(this, args);
    } catch (error) {
      call.error = error as Error;
      calls.push(call);
      throw error;
    }
    calls.push(call);
    return call.returned;
  } as Spy<Self, Args, Return>;
  Object.defineProperties(spy, {
    original: {
      enumerable: true,
      value: original,
    },
    calls: {
      enumerable: true,
      value: calls,
    },
    restored: {
      enumerable: true,
      get: () => false,
    },
    restore: {
      enumerable: true,
      value: () => {
        throw new MockError(
          "Cannot restore: function cannot be restored",
        );
      },
    },
  });
  return spy;
}

/**
 * Creates a session that tracks all mocks created before it's restored.