const test = require("ava");
const td = require("testdouble");

const reducer = async (state) => {
  const existing = await state.foo();
  console.log("existing:", existing);
};

test("foo", async (t) => {
  const foo = td.func(".foo");

  const state = td.object({
    foo
  });

  td.when(foo()).thenResolve({
    id: "123"
  });

  await reducer(state);
});