[英]How to test an ES7 async function using mocha/chai/chai-as-promised
I have the following function to test: 我有以下功能来测试:
// ...
const local = new WeakMap();
export default class User {
// ...
async password(password) {
if (!password) return local.get(this).get('hash'); // remove this for security reasons!
if (password.length < 6) throw new Error('New password must be at least 6 characters long');
if (!password.match(passwordPattern)) throw new Error(`New password must match ${passwordPattern}`);
local.get(this).set('hash', await Password.hash(password));
}
// ...
}
Now I want to test this function with mocha , chai and chai-as-promised doing this test-case: 现在我想用mocha , chai和chai-as- promise来测试这个函数做这个测试用例:
import chai from 'chai';
import chaiAsPromised from 'chai-as-promised';
import User from '../../../server/User';
chai.use(chaiAsPromised);
const expect = chai.expect;
describe('.password()', () => {
const testuser = new User({username: 'Testuser', password: '123abc'});
// FINDME
it(`should throw when too short`, () => {
return expect(testuser.password('1a')).to.eventually.throw();
});
// ...
});
Look for the // FINDME
comment in the above code to get the context I'm referring to. 在上面的代码中查找
// FINDME
注释以获取我所指的上下文。
So what happens is that the test(s) do not wait for the async password()
function to finish. 所以会发生的是,测试不会等待async
password()
函数完成。 As I found out ECMAScript7 async functions immediatelly return a thenable, so it should be fine since chai-as-promised use exactly this feature. 当我发现ECMAScript7异步函数立即返回一个thenable时,所以它应该没问题,因为chai-as-promised正好使用了这个特性。 My guess is, that async functions don't throw errors into this said promise rather than throwing it into the enclosing function itself, not being able to capture it through
expect()
. 我的猜测是,异步函数不会将错误抛入此声明,而不是将其抛入封闭函数本身,而不能通过
expect()
捕获它。
For the eager folks: I transpile this code on-the-fly with babel using the following command: 对于热切的人:我使用以下命令在babel上动态编写此代码:
babel-node --experimental node_modules/mocha/bin/_mocha --watch --recursive -R spec --check-leaks
Update for Babel 6: Babel 6更新:
Using babel-node 6.4.0, the following worked: 使用babel-node 6.4.0,以下工作:
npm install --save-dev babel-preset-stage-0
Then run: 然后运行:
./node_modules/.bin/babel-node --presets stage-0 node_modules/mocha/bin/_mocha --
recursive -R spec --check-leaks
We solved this issue by replacing eventually.throw()
with .be.rejected
provided by chai-as-promised, since an async function
always returns a Promise. 我们通过用chai-as-
.be.rejected
提供的.be.rejected
替换.be.rejected
eventually.throw()
来解决这个问题,因为async function
总是返回一个Promise。 That wasn't clear to me in the first place. 首先,我不清楚这一点。 Have a look at the discussion on github if you like.
如果你愿意,可以看一下关于github的讨论。
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