angular 4 unit testing error `TypeError: ctor is not a constructor`

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)

This can be an error in the providers declarations.

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

Here is an example that fires the error :

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

The correct declaration is :

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

I had the exact same message when building my app with AOT.

My problem was not related to providers as @abahet suggested.

It was because I setup a new library which was not AOT compliant (and didn't have any provider either). The library in question had to export (I'm talking about Typescript export, not the one from Angular module) what was imported in the module (in this case, a component and a pipe).