單元測試nunit的通用htmlHelper方法

Question

我是nUnit的新手，我的任務是爲某些htmlhelper擴展方法創建單元測試。

我該如何着手爲以下方法創建單元測試？

public static MvcHtmlString EnumDropDownListForOrderBy<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, bool orderById, string firstElement = null, object htmlAttributes = null) 
    { 
     ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData); 

     Type enumType = GetNonNullableModelType(metadata); 
     IEnumerable<TEnum> values = Enum.GetValues(enumType).Cast<TEnum>(); 

     IEnumerable<SelectListItem> items = values.Select(value => new SelectListItem() 
     { 
      Text = value.GetAttributeFrom<DescriptionAttribute>(value.ToString()).Description, 
      Value = value.ToString(), 
      Selected = value.Equals(metadata.Model) 
     }); 

     IEnumerable<SelectListItem> itemsFiltered = items.Where(e => !string.IsNullOrEmpty(e.Text)).AsEnumerable(); 

     itemsFiltered = itemsFiltered.OrderBy(e => (orderById ? e.Text : e.Value)); 

     return htmlHelper.DropDownListFor(
      expression, 
      itemsFiltered, 
      firstElement, 
      htmlAttributes 
     ); 
    } 

任何幫助，將不勝感激

Answer 1

下面是你如何寫這個單元測試。請注意，由於您沒有指定您使用Mock對象框架，因此我將使用窮人技術，即hand written stubs and mocks。如果您使用Moq，還有另一種輔助方法。

請務必注意，爲了簡化代碼執行，我對擴展方法進行了一些更改，因此測試不會意外失敗。無論如何，檢查任何意外的行爲是一個很好的防禦性編程練習。

回到測試。

SUT（測試系統）

這是SUT（待測系統）的樣子和支持類型的模樣。 （請相應隨意修改你的需要）

public static class MyHtmlHelper 
{ 
    public static MvcHtmlString EnumDropDownListForOrderBy<TModel, TEnum> 
     (this HtmlHelper<TModel> htmlHelper, 
     Expression<Func<TModel, TEnum>> expression, 
     bool orderById, string firstElement = null, object htmlAttributes = null, 
     Func<ModelMetadata> fromLambFunc = null) 
    { 
     ModelMetadata metadata = 
     ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);  
     Type enumType = GetNonNullableModelType(metadata); 
     IEnumerable<TEnum> values = Enum.GetValues(enumType).Cast<TEnum>(); 

     IEnumerable<SelectListItem> items = 
      values.Select(value => new SelectListItem() 
     { 
      Text = GetText(value), 
      Value = value.ToString(), 
      Selected = value.Equals(metadata.Model) 
     }); 

     IEnumerable<SelectListItem> itemsFiltered = 
     items.Where(e => !string.IsNullOrEmpty(e.Text)).AsEnumerable(); 
     itemsFiltered = itemsFiltered.OrderBy(e => (orderById ? e.Text : e.Value)); 

     return htmlHelper.DropDownListFor 
     (expression, itemsFiltered, firstElement, htmlAttributes); 
    } 

    private static Type GetNonNullableModelType(ModelMetadata metadata) { 
     return typeof (SomeEnum); 
    } 

    private static string GetText<TEnum>(TEnum value) { 
     return value.GetAttributeFrom<DescriptionAttribute>(value.ToString()) != null 
      ? value.GetAttributeFrom<DescriptionAttribute>(value.ToString()).Description 
      : string.Empty; 
    } 
} 

public static class ExtensionMethodsAttr 
{ 
    public static T GetAttributeFrom<T>(this object instance, string propertyName) 
     where T : Attribute 
    { 
     var attrType = typeof(T); 
     var property = instance.GetType().GetProperty(propertyName); 

     return property != null ? 
     (T)property.GetCustomAttributes(attrType, false).First() : default(T) ; 
    } 
} 

public enum SomeEnum { A,} 

單元測試

[TestFixture] 
public class HtmlHelperTests 
{ 
    [Test] 
    public void EnumDropDownListForOrderBy_InvokeDropDownListFor_ReturnsExpectedSelectItemResult() 
    { 
     //Arrange 
     var expected = "<select id=\"Foo\" name=\"Foo\"></select>"; 
     var fakeHtmlHelper = CreateHtmlHelperStaticStubs 
     (new ViewDataDictionary(new FakeViewModel() {Foo = SomeEnum.A})); 
     //var fakeHtmlHelper = CreateHtmlHelperUsingMoq 
     (new ViewDataDictionary(new FakeViewModel(){Foo = SomeEnum.A})); 

     //Act 
     var result = fakeHtmlHelper.EnumDropDownListForOrderBy 
     (model => model.Foo, It.IsAny<bool>(), null, null, null); 

     //Assert 
     Assert.AreEqual(expected, result.ToString()); 
    } 


    private static HtmlHelper<FakeViewModel> 
     CreateHtmlHelperStaticStubs(ViewDataDictionary viewData) 
    { 
     var stubControllerContext = new ControllerContext(new FakeHttpContext(), new RouteData(), new FakeController()); 

     var stubViewContext = new ViewContext(stubControllerContext, new FakeView(), 
      new ViewDataDictionary(new FakeViewModel() { Foo = SomeEnum.A }), 
      new TempDataDictionary(), new TextMessageWriter()); 

     var fakeViewDataContainer = new FakeViewDataContainer(); 
     fakeViewDataContainer.ViewData = viewData; 

     return new HtmlHelper<FakeViewModel>(stubViewContext, fakeViewDataContainer); 
    } 

    //Moq version 
    private static HtmlHelper<FakeViewModel> 
     CreateHtmlHelperUsingMoq(ViewDataDictionary viewData) 
    { 
     var stubControllerContext = new Mock<ControllerContext>(); 
     stubControllerContext.Setup(x => x.HttpContext).Returns(new Mock<HttpContextBase>().Object); 
     stubControllerContext.Setup(x => x.RouteData).Returns(new RouteData()); 
     stubControllerContext.Setup(x => x.Controller).Returns(new Mock<ControllerBase>().Object); ; 

     var stubViewContext = new Mock<ViewContext>(); 
     stubViewContext.Setup(x => x.View).Returns(new Mock<IView>().Object); 
     stubViewContext.Setup(x => x.ViewData).Returns(viewData); 
     stubViewContext.Setup(x => x.TempData).Returns(new TempDataDictionary()); 

     var mockViewDataContainer = new Mock<IViewDataContainer>(); 

     mockViewDataContainer.Setup(v => v.ViewData).Returns(viewData); 

     return new HtmlHelper<FakeViewModel>(stubViewContext.Object, mockViewDataContainer.Object); 
    } 
} 


class FakeHttpContext : HttpContextBase 
{ 
    private Dictionary<object, object> _items = new Dictionary<object, object>(); 
    public override IDictionary Items { get { return _items; } } 
} 

class FakeViewDataContainer : IViewDataContainer 
{ 
    private ViewDataDictionary _viewData = new ViewDataDictionary(); 
    public ViewDataDictionary ViewData { get { return _viewData; } set { _viewData = value; } } 
} 

class FakeController : Controller { } 

class FakeView : IView 
{ 
    public void Render(ViewContext viewContext, System.IO.TextWriter writer) 
    { 
     throw new NotImplementedException(); 
    } 
} 

public class FakeViewModel { 
    public SomeEnum Foo { get; set; } 
}