node.js js 是否应该无法读取 null 的属性“应该”
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Should js Cannot read property 'should' of null
提问by zero_coding
i try to use the testing tool mocha in node. Consider the following test scenario
我尝试在 node.js 中使用测试工具 mocha。考虑以下测试场景
var requirejs = require('requirejs');
requirejs.config({
//Pass the top-level main.js/index.js require
//function to requirejs so that node modules
//are loaded relative to the top-level JS file.
nodeRequire: require
});
describe('Testing controller', function () {
it('Should be pass', function (done) {
(4).should.equal(4);
done();
});
it('Should avoid name king', function (done) {
requirejs(['../server/libs/validate_name'], function (validateName) {
var err_test, accountExists_test, notAllow_test, available_test;
validateName('anu', function (err, accountExists, notAllow, available) {
accountExists.should.not.be.true;
done();
});
});
});
});
as a testing result i have got:
作为测试结果，我得到了：
$ make test
./node_modules/.bin/mocha \
--reporter list
. Testing controller Should be pass: 0ms
1) Testing controller Should avoid name anu
1 passing (560 ms)
1 failing
1) Testing controller Should avoid name anu:
Uncaught TypeError: Cannot read property 'should' of null
at d:\townspeech\test\test.spec.js:23:30
at d:\townspeech\server\libs\validate_name.js:31:20
at d:\townspeech\test\test.spec.js:22:13
at Object.context.execCb (d:\townspeech\node_modules\requirejs\bin\r.js:1869:33)
at Object.Module.check (d:\townspeech\node_modules\requirejs\bin\r.js:1105:51)
at Object.Module.enable (d:\townspeech\node_modules\requirejs\bin\r.js:1376:22)
at Object.Module.init (d:\townspeech\node_modules\requirejs\bin\r.js:1013:26)
at null._onTimeout (d:\townspeech\node_modules\requirejs\bin\r.js:1646:36)
at Timer.listOnTimeout [as ontimeout] (timers.js:110:15)
make: *** [test] Error 1
The first pass without any complication but the second, it seems like, that could not attach module shouldjs. Why?
第一遍没有任何复杂性，但第二遍似乎无法附加模块 shouldjs。为什么？
采纳答案by Golo Roden
That's a known problem with the shouldlibrary: As it extends object, of course it only works when you have a concrete object. As null, by definition, means that you don't have an object, you can not call any methods on it or access any of its properties.
这是should库的一个已知问题：当它扩展时object，当然只有当你有一个具体的对象时它才有效。因为null，根据定义，意味着您没有对象，您不能对其调用任何方法或访问其任何属性。
Hence, shouldis not available in this case.
因此，should在这种情况下不可用。
Basically, you have two options of how to deal with this:
基本上，您有两种处理方法：
- You could exchange
actualandexpected. This way, as long as you do not expectnull, you have an object in the beginning and hence can access itsshouldproperty. But, this is not nice, as it changes semantics, and does not work in all cases. - You could exchange the
shouldlibrary by another assertion library that does not have this problem.
- 你可以交换
actual和expected。这样，只要您不期望null，您在开始时就有一个对象，因此可以访问其should属性。但是，这并不好，因为它改变了语义，并且不适用于所有情况。 - 您可以
should通过另一个没有此问题的断言库来交换库。
Personally, I'd go with option 2, and my highly subjective personal favorite for this is node-assertthat(which has been written by me, hence it's my favorite).
就我个人而言，我会选择选项 2，而我对此高度主观的个人最喜欢的是node-assertthat（这是我写的，因此它是我的最爱）。
Anyway, there are lots of other options, such as expect. Feel free to use any of these assertion libraries that best suits your style of writing tests.
无论如何，还有很多其他选项，例如expect。随意使用任何最适合您编写测试风格的断言库。
回答by Henry Tao
I had the same problem. I solved it by using:
我有同样的问题。我通过使用解决了它：
(err === null).should.be.true;
(err === null).should.be.true;
回答by agebrock
You can use should directly
你可以直接使用 should
should.not.exist(err);
回答by Mbrevda
One more option that I don't see mentioned here:
我没有看到这里提到的另一种选择：
should(err === null).be.null
In you example that would would be:
在你的例子中，这将是：
should(accountExists).be.null
回答by Jeff C
I always find expectworks better with nulland undefinedas follows:
我总是发现expect使用null和效果更好，undefined如下所示：
expect(err).be.null
expect(err).be.null
