Angular 4单元测试错误 `TypeError: ctor is not a constructor`

Question

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 并且不知道为什么在 typescript 编译时没有错误时会发生这种情况。

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)

Answer 1

这可能是提供者声明中的错误。

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”。

这是一个引发错误的例子:

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

正确的声明是:

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