摩卡异步测试句柄错误 [英] Mocha async test handle errors

问题描述

我正在尝试用Mocha创建一个测试用例，但是我的代码是异步的.

I'm trying to create a test case with Mocha but my code is asynchronous.

很好，我可以在"it"上添加一个完成"的回调函数，对于肯定的情况，它可以很好地工作.但是，当尝试测试否定案例时，只会使测试失败.

That's fine, I can add a "done" callback function to "it" and that will work perfectly fine for positive cases. But when trying to test negative cases, it will just make the test fail.

我想做这样的事情，但要异步:

I would like to make something like this but asynchronous:

someObject.someMethod(null).should.equal(false)

相反，我只能测试返回的回调，而不能测试实际发生的情况(null无效):

Instead I can only test for a callback to return, instead of testing what really happend (null is not valid):

it('this should return false or an error', function(done) {
    someObject.someMethod(null, '', done);
});

我想写这样的东西:

it('this should return false or an error', function(done) {
    someObject.someMethod(null, '', done).should.throw();
});

但这会导致此错误:

"TypeError: Cannot read property 'should' of undefined"

我也尝试使用Expect和assert，但是同样的规则适用.

I also tried using expect and assert, but the same rules apply.

有任何线索吗? 谢谢

编辑#1:

我尝试失败:

使用true/false

Using true/false

return (true); // ok
retur (false); // error

使用回调:

callback(); // ok
callback(err); // error

使用callback2:

Using callback2:

callback(true); // ok
callback(false); // error

使用callback3:

Using callback3:

callback(null); // ok
callback(new Error()); // error

使用抛出(也在try/catch块中):

Using throw (also inside a try/catch block):

// a
 throw new Error();
callback();  

// b
 throw new Error();
callback(new Error());  

// c
 throw new Error();
callback(false);  

我还尝试了几种组合，例如返回和调用回调，成功返回但在错误时抛出或调用回调，反之亦然.

I have also tried several combinations such as returning and calling a callback, returning on success but throwing or calling a callback on error and conversely..

编辑#2:

it('should throw', function(done) {
  (function(done) {
    someObject.someMethod(null, '', done)
  }).should.throw();
});`

编辑#3:

要总结在测试方面:

it('this should return false or an error', function(done) {
    someObject.someMethod(null, function(err, value) {
        expect(value === false || err instanceof Error).toEqual(true);
       return done();
    });
}); 

在代码端:function(var，callback)

And on the code-side: function(var, callback)

...
callback(new Error('your comments'), false);
// or
callback(new Error('your comments'));
...
// if successful:
callback();
// or
callback(null);
// or
callback(null, 'foo');

推荐答案

假定someObject.someMethod遵守常规的Node.js回调约定(错误作为第一个参数，值作为第二个参数)，则可以使用以下内容: /p>

Assuming that someObject.someMethod adheres to the regular Node.js callback convention (error as first argument, value as second), you could use something like this:

it('this should return false or an error', function(done) {
  someObject.someMethod(null, '', function(err, value) {
    (err instanceof Error || value === false).should.equal(true);
    return done();
  });
});

我从测试用例的名称推断出要在两种情况下进行测试:方法是返回"错误，或者是返回"值false(通过使用适当的参数).

I inferred from the name of the test case that you want to test for two situations: either the method is "returning" an error, or it's "returning" a value of false (by calling the callback function with the appropriate arguments).

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