我遇到了ES6 Promise和一些mocha / chai测试的奇怪行为 . 考虑以下 foo()
函数返回一个promise,我想测试两件事:
-
它返回一个promise(所以,一个对象)
-
它在失败时抛出异常(以及对象) .
问题是,在测试 expect(..).to.be.an('object')
两种情况下都失败了,但类型 is object
(用 typeof
检查) .
这是我的代码:
var chai = require('chai');
var expect = chai.expect;
var foo = function (a, b) {
return new Promise(function(resolve, reject) {
if (a < b) {
resolve();
}
else {
throw new Error('failed');
}
});
}
describe('foo function', function () {
it('should return a promise', function () {
var call = foo();
//typeof call: object
expect(call).to.be.defined; //pass
expect(call).to.be.an('object'); //fail
expect(call.then).to.be.a('function'); //pass
});
it('should throw an exception on failure', function () {
return foo().catch(function (e) {
//typeof e: object
expect(e).to.be.defined; //pass
expect(e).to.be.an('object'); //fail
});
})
});
你有什么线索来解释这个吗?
如果它可以帮助,这里是摩卡调用的结果 mocha test.js
foo function
1) should return a promise
2) should throw an exception on failure
0 passing (20ms)
2 failing
1) foo function should return a promise:
AssertionError: expected {} to be an object
at Context.<anonymous> (test.js:34:24)
2) foo function should throw an exception on failure:
AssertionError: expected [Error: failed] to be an object
at test.js:42:23
1 回答
Chai使用type-detect for
a/an
,这在输入对象时很聪明(取决于你如何看待它) .例如:
所以这将使你的测试通过:
要么是,要么使用.instanceOf():