title: error: Failed: Template parse errors: 'mat-checkbox' is not a known element
body: <p>I create this code for testing my component.</p>
  
  <p>I tried this code:</p>
  
  <pre><code>describe('Component: AddAlarms', () =&gt; {
      let component: AddAlarmsFormComponent;
      let fixture: ComponentFixture&lt;AddAlarmsFormComponent&gt;;
      beforeEach(() =&gt; {
          TestBed.configureTestingModule({
              declarations: [AddAlarmsFormComponent]
          });
          fixture = TestBed.createComponent(AddAlarmsFormComponent);
          component = fixture.componentInstance;
      });
  });
  </code></pre>
  
  <p>when run <code>ng test</code> show this error:</p>
  
  <pre><code>Failed: Template parse errors:
  'mat-checkbox' is not a known element:
  1. If 'mat-checkbox' is an Angular component, then verify that it is part of this module.
  2. If 'mat-checkbox' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message. ("
          &lt;/div&gt;
          &lt;div class="input-field col s2"&gt;
            [ERROR -&gt;]&lt;mat-checkbox class="example-margin" (click)="sortbydate()"&gt;Dates&lt;/mat-checkbox&gt;
          &lt;/div&gt;
       "): ng:///DynamicTestModule/NotificationsComponent.html@12:10
  </code></pre>
  
  <p>I verify my module.ts and it's ok.  So, I have this:</p>
  
  <pre><code>import {MatCheckboxModule} from '@angular/material/checkbox';
  </code></pre>
  
  <p>Can you tell me, what is the problem?</p>