Question

我正在试图监视已经通过Jest传递给异步函数的参数。

我非常简单的模块......

// data_loader.js
import axios from "axios";

export const data_loader = ( options ) => {
    return axios( generateUrl( options ) )
        .then( response => response.data );
};

和我的考试......

// data_loader.test.js
import * as data_loader from "./data_loader";

// this spies on the "load" function and passes
it("should be called once", () => { 
    const spy = data_loader.load = jest.fn();
    data_loader.load(options);
    expect(spy).toHaveBeenCalledTimes(1);
});

// here's where i'm trying to spy on axios to see if it is called with appropriate arguments 
it("axios should be called with the supplied options", () => {
    // have tried all syntax under the sun
});

如果我理解正确，我相信我需要嘲笑axios，因为没有理由需要真正调用它来检查它收到的论据。

我已经尝试了jest.mock("axios")，jest.spyOn("axios")和一些针对Axios的模拟库，但我无法理解语法。

Answer 1

经过多次尝试后，我应该学会RTFM。

在调用data_loader.load函数之前，我使用axios-mock-adapter来模拟调用。我还修改了load函数以返回一个promise 。

然后，您可以通过回复来电来声明承诺的结果。这似乎是Jest知道等待的方式。

模块......

// data_loader.js
import axios from "axios";

export const load = (options) => {
    return new Promise((resolve, reject) => {
        axios(generateUrl(options))
            .then(response => {
                resolve(response);
            })
            .catch(err => {
                reject(err);
            });
    });
};

和测试...

// data_loader.test.js
import axios from "axios"; // we need to import this so the mocking library can wrap it
import MockAdapter from "axios-mock-adapter";

const mock = new MockAdapter(axios); // wrap the real axios with the fake axios

it("axios should be called with the generated url", () => {
    expect.assertions(1); // tell Jest that we're expecting one assertion
    mock.onAny().reply(200, {}); // use the mock on any call to axios
    return loader.load(...options).then(response => { // "return" is vital here - jest won't wait without it
        expect(response.config.url)
            .toBe("/my-generated-url");
    });
});

开玩笑 - 窥探嵌套承诺（axios）

1 个答案: