Angular: How to mock MatDialogRef while testing

I solved it by changing the component constructor to:

constructor(
  public dialogRef: MatDialogRef<CustomDialogComponent>,
  @Inject(MAT_DIALOG_DATA) public data: Dialog | any
)

The providers in the TestBed were:

providers: [{ provide: MatDialogRef, useValue: {} }, { provide: MAT_DIALOG_DATA, useValue: data }]

If you use at least one MatDialogRef method, you should create a mock. For example I use the close() method. Without it errors would be generated so I made the below class with an empty method.

export class MatDialogRefMock {
    close(value = '') {

    }
}

and use that instead of an empty value, with useClass

{ provide: MatDialogRef, useClass: MatDialogRefMock },

Import MatDialogModule and MatDialogRef from angular/material/dialog instead of angular/material. Import the ModalDialogModule and provide providers for MatDialogRef in your TestBed.

Import {MatdialogModule,MatDialogRef} from '@angular/material/dialog';

TestBed.configureTestingModule({
declarations: [componentName],
imports: [MatdialogModule],
providers: [{provide : MatDialogRef, useValue : {}}]
});