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 }]