Javascript 如何在 ES6 中存根导出的函数？
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How to stub exported function in ES6?
提问by Mike Chaliy
I have file foo.js:
我有文件 foo.js：
export function bar (m) {
console.log(m);
}
And another file that uses foo.js, cap.js:
另一个使用 foo.js 的文件 cap.js：
import { bar } from 'foo';
export default m => {
// Some logic that I need to test
bar(m);
}
I have test.js:
我有 test.js：
import cap from 'cap'
describe('cap', () => {
it('should bar', () => {
cap('some');
});
});
Somehow I need override implementation of bar(m)in test. Is there any way to do this?
不知何故，我需要覆盖bar(m)测试中的实现。有没有办法做到这一点？
P.S. I use babel, webpack and mocha.
PS 我使用 babel、webpack 和 mocha。
回答by Mike Chaliy
Ouch.. I found solution, so I use sinonto stub and import * as foo from 'foo'to get object with all exported functions so I can stub them.
哎哟..我找到了解决方案，所以我使用sinon存根并import * as foo from 'foo'获取所有导出函数的对象，以便我可以存根它们。
import sinon from 'sinon';
import cap from 'cap';
import * as foo from 'foo';
sinon.stub(foo, 'bar', m => {
console.log('confirm', m);
});
describe('cap', () => {
it('should bar', () => {
cap('some');
});
});
回答by DreamSonic
You can replace/rewrite/stub exports only from within the module itself. (Here's an explanation)
您只能从模块本身内部替换/重写/存根导出。（这里有一个解释）
If you rewrite 'foo.js' like this:
如果你像这样重写'foo.js'：
var bar = function bar (m) {
console.log(m);
};
export {bar}
export function stub($stub) {
bar = $stub;
}
You can then override it in your test like this:
然后，您可以像这样在测试中覆盖它：
import cap from 'cap'
import {stub} from 'foo'
describe('cap', () => {
it('should bar', () => {
stub(() => console.log('stubbed'));
cap('some'); // will output 'stubbed' in the console instead of 'some'
});
});
I've created a Babel plugin that transforms all the exports automatically so that they can be stubbed: https://github.com/asapach/babel-plugin-rewire-exports
我创建了一个 Babel 插件，可以自动转换所有导出，以便它们可以被存根：https: //github.com/asapach/babel-plugin-rewire-exports
回答by Daniel Conde Marin
While @Mike solution would work in old versions of sinon, it has been removed since sinon 3.0.0.
虽然@Mike 解决方案适用于旧版本的 sinon，但它已从 sinon 3.0.0 中删除。
Now instead of:
现在代替：
sinon.stub(obj, "meth", fn);
you should do:
你应该做：
stub(obj, 'meth').callsFake(fn)
Example of mocking google oauth api:
模拟 google oauth api 的示例：
import google from 'googleapis';
const oauth2Stub = sinon.stub();
sinon.stub(google, 'oauth2').callsFake(oauth2Stub);
oauth2Stub.withArgs('v2').returns({
tokeninfo: (accessToken, params, callback) => {
callback(null, { email: '[email protected]' }); // callback with expected result
}
});
回答by qff
You can use babel-plugin-rewire(npm install --save-dev babel-plugin-rewire)
你可以使用babel-plugin-rewire( npm install --save-dev babel-plugin-rewire)
And then in test.jsuse the __Rewire__function on the imported module to replace the function in that module:
然后test.js使用__Rewire__导入模块上的函数来替换该模块中的函数：
// test.js
import sinon from 'sinon'
import cap from 'cap'
describe('cap', () => {
it('should bar', () => {
const barStub = sinon.stub().returns(42);
cap.__Rewire__('bar', barStub); // <-- Magic happens here
cap('some');
expect(barStub.calledOnce).to.be.true;
});
});
Be sure to add rewireto your babel plugins in .babelrc:
一定要添加rewire到你的 babel 插件中.babelrc：
// .babelrc
{
"presets": [
"es2015"
],
"plugins": [],
"env": {
"test": {
"plugins": [
"rewire"
]
}
}
}
Lastly, as you can see the babel-plugin-rewireplugin is only enabled in the test environment, so you should call you test runner with the BABEL_ENVenvironment variable set to test(which you're probably doing already):
最后，正如您所看到的，该babel-plugin-rewire插件仅在测试环境中启用，因此您应该调用测试运行程序并将BABEL_ENV环境变量设置为test（您可能已经这样做了）：
env BABEL_ENV=test mocha --compilers js:babel-core/register test-example.js
Note: I couldn't get babel-plugin-rewire-exportsto work.
注意：我无法babel-plugin-rewire-exports上班。
