docs: add content to mocking-localizer.md

* Update mocking-localizer.md

* Update mocking-localizer.md

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docs/site/docs/test-doubles/mocking-localizer.md

@@ -3,4 +3,12 @@ uid: mocking-localizer
 title: Mocking Localization via IStringLocalizer
 ---
 
-# Mocking Localization via `IStringLocalizer`
+<p>There are just two steps. First in your setup add the following:</p>
+```csharp
+TestContext.Services.AddLocalization();
+```
+<p>Then in your test code, when you need the localized string to compare, you write the following:</p>
+```csharp
+var localizer = ctx.Services.GetService<IStringLocalizer<SharedStrings>>();
+  ```
+<p>Where SharedStrings.cs (you can name this anything you want) that has the resource files such as `SharedStrings.en.resx`</p>