Cuando ejecuto Karma para probar mi aplicación Angular4, aparece este errorFound the synthetic property @enterAnimation. Please include either "BrowserAnimationsModule" or "NoopAnimationsModule" in your application. aunque ya importé el módulo enapp.module.ts

        // animation module
        import { BrowserAnimationsModule } from '@angular/platform-browser/animations'; 
    ...
@NgModule({
    imports: [...
        BrowserAnimationsModule,
        ...
      ],

y en micomponente:

 import { Component, OnInit } from '@angular/core';
    import {
      trigger,
      state,
      style,
      animate,
      transition
    } from '@angular/animations';

    @Component({
      selector: 'app-about',
      animations: [
        trigger(
          'enterAnimation', [
            transition(':enter', [
              style({ transform: 'translateX(100%)', opacity: 0 }),
              animate('500ms', style({ transform: 'translateX(0)', opacity: 1 }))
            ]),
            transition(':leave', [
              style({ transform: 'translateX(0)', opacity: 1 }),
              animate('500ms', style({ transform: 'translateX(100%)', opacity: 0 }))
            ])
          ]
        ),
        trigger(
          'enterAnimationVetically', [
            transition(':enter', [
              style({ transform: 'translateY(100%)', opacity: 0 }),
              animate('500ms', style({ transform: 'translateY(0)', opacity: 1 }))
            ]),
            transition(':leave', [
              style({ transform: 'translateY(0)', opacity: 1 }),
              animate('500ms', style({ transform: 'translateY(100%)', opacity: 0 }))
            ])]
        )
      ],
...

La aplicación funciona perfectamente conng serve sin embargo, recibí este error con karma.