Faking IWebAssemblyHostEnvironment

bUnit has a fake implementation of Blazor's IWebAssemblyHostEnvironment built-in, which is added by default to bUnit's TestContext.Services service provider. That means nothing special is needed to test components that depend on IWebAssemblyHostEnvironment, as it is already available by default.

Out of the box, the fake implementation has its Environment property set to production, and its BaseAddress set to /.

Setting Environment and BaseAddress

Lets look at a few examples of how to set the two IWebAssemblyHostEnvironment properties Environment and BaseAddress via the built-in fake.

In the examples, we'll use the following <HelloWorld> component:

@inject IWebAssemblyHostEnvironment HostEnvironment

<p id="message">
  Hello @(HostEnvironment.IsDevelopment() ? "Developers" : "World"). 
</p>
<p id="address">
  The base URL is: @HostEnvironment.BaseAddress
</p>

To verify that the <HelloWorld> component correctly says hello to the developers, do the following:

// Arrange
var hostEnvironment = Services.GetRequiredService<FakeWebAssemblyHostEnvironment>();

// Sets the environment to "Development". There are two other helper 
// methods available as well, SetEnvironmentToProduction() and 
// set SetEnvironmentToStaging(), or environment can also be changed
// directly through the hostEnvironment.Environment property.
hostEnvironment.SetEnvironmentToDevelopment();

var cut = RenderComponent<SimpleUsingWebAssemblyHostEnvironment>();

// Assert - inspects markup to verify the message
cut.Find("#message").MarkupMatches($"<p>Hello Developers.</p>");

To verify that the <HelloWorld> component correctly uses the current BaseAddress, do the following:

// Arrange
var hostEnvironment = Services.GetRequiredService<FakeWebAssemblyHostEnvironment>();

// Sets a new base address directly on the BaseAddress property.
hostEnvironment.BaseAddress = "myBaseUrl/";

// Act
var cut = RenderComponent<SimpleUsingWebAssemblyHostEnvironment>();

// Assert - inspect markup to verify that the BaseAddress is used correctly.
cut.Find("#address").MarkupMatches($"<p>The base URL is: myBaseUrl/</p>");