node . js 中的存根是什么？
一种小的程序例行程序，它代替一个较长的程序，该程序以后可能被装入或位于远处。
存根的特征:
- 存根可以是匿名的。
- 存根可以打包到现有函数中。当我们将一个存根打包到现有函数中时，原始函数不会被调用。
- 存根是影响组件或模块行为的函数或程序。
- 存根是测试的虚拟对象。
- 存根实现预编程的响应。
示例:
var fs = require('fs')
var writeFileStub = sinon.stub(fs,
'writeFile', function (path, data, cb) {
return cb(null)
})
expect(writeFileStub).to.be.called
writeFileStub.restore()
什么时候用存根？
- 防止直接调用特定的方法。
- 控制从测试到强制代码的特定路径上的方法行为。例如:错误处理。
- 替换有问题的代码。
- 测试异步代码很容易。
创建引发异常的异步存根的示例:
require("@fatso83/mini-mocha").install();
const sinon = require("sinon");
const PubSub = require("pubsub-js");
const referee = require("@sinonjs/referee");
const assert = referee.assert;
describe("PubSub", function() {
it("Calling all the subscribers,
irrespective of exceptions.", function() {
const message = "an example message";
const stub = sinon.stub().throws();
const spy1 = sinon.spy();
const spy2 = sinon.spy();
const clock = sinon.useFakeTimers();
PubSub.subscribe(message, stub);
PubSub.subscribe(message, spy1);
PubSub.subscribe(message, spy2);
assert.exception(()=>{
PubSub.publishSync(message, "some data");
clock.tick(1);
});
assert.exception(stub);
assert(spy1.called);
assert(spy2.called);
assert(stub.calledBefore(spy1));
clock.restore();
});
});
输出:
Calling all the subscribers, irrespective of exceptions.
Stubs 的例子:让我们考虑一个购买商品的电子商务网站的例子。如果我们成功了，我们将向客户发送一封邮件。
const purchaseItems(cartItems, user)=>{
let payStatus = user.paymentMethod(cartItems)
if (payStatus === "successful") {
user.SuccessMail()
} else {
user.redirect("error_page_of_payment")
}
}
}
function() {
// Mail will be send for successful payment.
let paymentStub = sinon.stub().returns("successful")
let mailStub = sinon.stub(
let user = {
paymentMethod: paymentStub,
SuccessMail: mailStub
}
purchaseItems([], user)
assert(mailStub.called)
}
示例 1: 执行存根的简单示例。
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<div id="mocha"></div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<script>
mocha.setup('bdd');
function saveUser(user, callback) {
$.post('/users', {
first: user.firstname,
last: user.lastname
}, callback);
}
describe('saveUser', function () {
it('should call callback after saving',
function () {
// We'll stub $.post so a
// request is not sent
var post = sinon.stub($, 'post');
post.yields();
// We can use a spy as the callback
// so it's easy to verify
var callback = sinon.spy();
saveUser({ firstname: 'Han',
lastname: 'Solo' }, callback);
post.restore();
sinon.assert.calledOnce(callback);
});
});
mocha.run();
</script>
</head>
</html>
输出:
例 2:
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<h1>GeeksForGeeks</h1>
<div id="mocha"></div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<script>
mocha.setup('bdd');
function saveUser(user, callback) {
$.post('/users', {
first: user.firstname,
last: user.lastname
}, callback);
}
describe('saveUser', function () {
it(
'It will send the correct parameters to the expected URL',
function () {
// We'll stub $.post same as before
var post = sinon.stub($, 'post');
// We'll set up some variables to
// contain the expected results
var expectedUrl = '/users';
var expectedParams = {
first: 'Expected first name',
last: 'Expected last name'
};
// We can also set up the user we'll
// save based on the expected data
var user = {
firstname: expectedParams.first,
lastname: expectedParams.last
}
saveUser(user, function () { });
post.restore();
sinon.assert.calledWith(post,
expectedUrl, expectedParams);
});
});
mocha.run();
</script>
</head>
</html>
输出:
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