title: Angular7: NullInjectorError: No provider for FormGroup
body: <p>I'm getting really fustrated because I have no idea what's happening. 
  Everything worked correctly this morning right before some changes I made to merge together 2 forms in a ReactiveForm and now I get the following error in the browser: </p>
  
  <blockquote>
    <p>Error: StaticInjectorError(AppModule)[FormGroup]:<br>
    StaticInjectorError(Platform: core)[FormGroup]: 
        NullInjectorError: No provider for FormGroup! Error: StaticInjectorError(AppModule)[FormGroup]:<br>
    StaticInjectorError(Platform: core)[FormGroup]: 
        NullInjectorError: No provider for FormGroup!</p>
  </blockquote>
  
  <p>I'm importing <code>FormsModule</code> and <code>ReactiveFormsModule</code> in my <code>app.module.ts</code> file: </p>
  
  <pre><code>import { BrowserModule } from '@angular/platform-browser';
  import { NgModule } from '@angular/core';
  import { FormsModule, ReactiveFormsModule } from '@angular/forms';
  [...]
  @NgModule({
    declarations: [
      AppComponent,
      CustomersComponent,
      HeaderComponent,
      CustomersListComponent,
      CustomerEditComponent
    ],
    imports: [
      BrowserModule,
      AppRoutingModule,
      FormsModule,
      ReactiveFormsModule,
      ...
      HttpClientModule
    ],
    providers: [],
    bootstrap: [AppComponent]
  })
  export class AppModule { }
  </code></pre>
  
  <p>And then the FormGroup in my component: </p>
  
  <pre><code>import { FormGroup, FormControl, Validators } from '@angular/forms';
  [...]
  </code></pre>
  
  <p>And declaring a new FormGroup afterwards in the component.
  I tried to reinstall the <code>@angular/forms</code> package with npm but I'm still getting the error... 
  I've seen some similar questions asked but from what I could tell, it was related with the testing environment. If you have any idea, thanks in advance.</p>