public void SetVernacularMaterialsAndContentType_IncompatibleWithAudience_ThrowsInvalidOperationException()
 {
     _helper.SetAudience(AudienceType.Training);
     Assert.Throws <InvalidOperationException>(
         () => _helper.SetVernacularMaterialsAndContentType(VernacularMaterialsType.BibleBackground)
         );
 }