ViewBag, ViewData & TempData

The "Music Store" web application does use only the "ViewBag" so we will write some tests for it. The "ViewData" and the "TempData" use similar syntax.

Testing with ViewBag entry

Let's test something simple - the HTTP Get overload of the "Login" action in the "AccountController":

public IActionResult Login(string returnUrl = null)
{
    ViewBag.ReturnUrl = returnUrl;
    return View();
}

We need a new dependency (seriously, stop it with these dependencies) - "MyTested.AspNetCore.Mvc.ViewData":

<!-- Other ItemGroups -->

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.0.1" />
    <PackageReference Include="Moq" Version="4.13.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Authentication" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Caching" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Controllers" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Controllers.ActionResults" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Controllers.Attributes" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Controllers.Views" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Controllers.Views.ActionResults" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.DependencyInjection" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.EntityFrameworkCore" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Http" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Models" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.ModelState" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Options" Version="2.2.0" />
    <PackageReference Include="MyTested.AspNetCore.Mvc.Session" Version="2.2.0" />
    <!-- MyTested.AspNetCore.Mvc.ViewData package -->
    <PackageReference Include="MyTested.AspNetCore.Mvc.ViewData" Version="2.2.0" />
    <PackageReference Include="xunit" Version="2.4.0" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
  </ItemGroup>

<!-- Other ItemGroups -->

We need to add the "ViewData" features, because the "ViewBag" is actually a dynamic version of it.

I hope you remember how we tested session and cache. Well, the "ViewBag" ("ViewData" and "TempData" too) is no different:

[Theory]
[InlineData("Test/Return/Url")]
public void LoginShouldHaveReturnUrlInTheViewBag(string returnUrl)
    => MyController<AccountController>
        .Instance()
        .Calling(c => c.Login(returnUrl))
        .ShouldHave()
        .ViewBag(viewBag => viewBag // <---
            .ContainingEntry("ReturnUrl", returnUrl))
        .AndAlso()
        .ShouldReturn()
        .View();

Testing with multiple ViewBag entries

Let's write another one - for the HTTP Get overload of the "Create" action in "StoreManagerController":

public IActionResult Create()
{
    ViewBag.GenreId = new SelectList(DbContext.Genres, "GenreId", "Name");
    ViewBag.ArtistId = new SelectList(DbContext.Artists, "ArtistId", "Name");
    return View();
}

And our test:

[Fact]
public void CreateShouldHaveValidEntriesInViewBag()
{
    var genres = new[]
    {
        new Genre { GenreId = 1, Name = "Rock" },
        new Genre { GenreId = 2, Name = "Rap" }
    };

    var artists = new[]
    {
        new Artist { ArtistId = 1, Name = "Tupac" },
        new Artist { ArtistId = 2, Name = "Biggie" }
    };

    MyController<StoreManagerController>
        .Instance()
        .WithData(genres)
        .WithData(artists)
        .Calling(c => c.Create())
        .ShouldHave()
        .ViewBag(viewBag => viewBag // <---
            .ContainingEntries(new
            {
                GenreId = new SelectList(
                    From.Services<MusicStoreContext>().Genres, "GenreId", "Name"),

                ArtistId = new SelectList(
                    From.Services<MusicStoreContext>().Artists, "ArtistId", "Name")
            }))
        .AndAlso()
        .ShouldReturn()
        .View();
}

The "ContainingEntries" call is equivalent to this one:

.ContainingEntries(new Dictionary<string, object>
{
    ["GenreId"] = new SelectList(
        From.Services<MusicStoreContext>().Genres, "GenreId", "Name"),

    ["ArtistId"] = new SelectList(
        From.Services<MusicStoreContext>().Artists, "ArtistId", "Name")
}))

Both methods will validate whether the total number of entries in the "ViewBag" is equal to the total number you provide in the test. For a sanity check - remove the "ArtistId" property from the anonymous object and run the test again:

When calling Create action in StoreManagerController expected view bag to have 1 entry, but in fact found 2.

If you do not want the total number of entries validation, just use:

.ViewBag(viewBag => viewBag // <---
    .ContainingEntry("GenreId", new SelectList(
        From.Services<MusicStoreContext>().Genres, "GenreId", "Name"))
    .ContainingEntry("ArtistId", new SelectList(
        From.Services<MusicStoreContext>().Artists, "ArtistId", "Name")))

ViewData and TempData

"ViewData" has the same API:

MyController<SomeController>
    .Instance()
    .Calling(c => c.SomeAction())
    .ShouldHave()
    .ViewData(viewData => viewData // <---
        .ContainingEntry("SomeKey", someValue))
    .AndAlso()
    .ShouldReturn()
    .View();

"TempData" too, but you will need the "MyTested.AspNetCore.Mvc.TempData" package:

MyController<SomeController>
    .Instance()
    .Calling(c => c.SomeAction())
    .ShouldHave()
    .TempData(tempData => tempData // <---
        .ContainingEntry("SomeKey", someValue))
    .AndAlso()
    .ShouldReturn()
    .View();

Additionally, you can populate the "TempData" dictionary before the actual action call:

MyController<SomeController>
    .Instance()
    .WithTempData(tempData => tempData
        .WithEntry("SomeKey", someValue))
    .Calling(c => c.SomeAction())
    .ShouldReturn()
    .View();

Section summary

We saw how easy it is to test with "ViewBag", "ViewData" and "TempData". Their fluent assertion APIs are very similar to the "Session" and the "Cache" ones. But enough about controllers, let's finally move on to View Components!