How to Avoid NullReferenceException When Mocking HttpContext.Current.Session in Unit Tests?

Resolving NullReferenceException Issues When Mocking HttpContext.Current.Session in Unit Tests

Unit testing web services that rely on HttpContext.Current.Session often leads to NullReferenceException errors. This article presents a solution for initializing the session within your unit tests.

To simulate the ASP.NET runtime environment during testing, we'll construct a mock HttpContext object that replicates session behavior. This involves creating a mock HttpRequest, a StringWriter for the HTTP response, and then assembling a HttpContext using these components.

Subsequently, a session container needs to be created and initialized using AddHttpSessionStateToContext. This mimics the session management process of a real web request.

By assigning this mock context to HttpContext.Current, our unit tests can access the session as if running within the web application. This allows setting session values without encountering the NullReferenceException:

<code class="language-csharp">HttpContext.Current = MockHelper.FakeHttpContext();
HttpContext.Current.Session["CustomerId"] = "customer1";
HttpContext.Current.Session["CustomerUrl"] = "customer1Url";</code>

This method enables thorough testing of code interacting with HttpContext.Current.Session, ensuring robust testing of your web services.

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