angular 4 单元测试错误`TypeError: ctor is not a constructor` [英] angular 4 unit testing error `TypeError: ctor is not a constructor`

问题描述

我正在尝试测试我的路由解析器，在测试时我得到了 TypeError: ctor is not a constructor 并且不知道为什么会在打字稿编译时没有错误时发生.

I am trying to test my route resolver and while testing I got TypeError: ctor is not a constructor and no idea why it happen while typescript compile time no error.

TypeError: ctor is not a constructor
TypeError: ctor is not a constructor
    at _createClass (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42355:26)
    at _createProviderInstance$1 (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42330:26)
    at resolveNgModuleDep (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42315:17)
    at _createClass (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42362:26)
    at _createProviderInstance$1 (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42330:26)
    at resolveNgModuleDep (http://localhost:9877/_karma_webpack_/vendor.bundle.js:42315:17)
    at NgModuleRef_.webpackJsonp../node_modules/@angular/core/@angular/core.es5.js.NgModuleRef_.get (http://localhost:9877/_karma_webpack_/vendor.bundle.js:43401:16)
    at TestBed.webpackJsonp../node_modules/@angular/core/@angular/core/testing.es5.js.TestBed.get (http://localhost:9877/_karma_webpack_/vendor.bundle.js:48412:47)
    at http://localhost:9877/_karma_webpack_/vendor.bundle.js:48418:61
    at Array.map (native)

推荐答案

这可能是提供程序声明中的错误.

This can be an error in the providers declarations.

当您尝试模拟提供者并使用 useClass 而不是 useValue 时，会触发错误TypeError: ctor is not a constructor".

When you try to mock a provider and use useClass instead of useValue the error "TypeError: ctor is not a constructor" is fired.

这是一个触发错误的例子:

Here is an example that fires the error :

providers: [{provide: OrderService, useClass: new OrderServiceMock()}]

正确的声明是:

providers: [{provide: OrderService, useValue: new OrderServiceMock()}]

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