Substitute a sealed class
c#, nsubstitute, unit-testing
Solution
Instead of trying to find a way to fake a `sealed` object, I'd instead look to see if I can get a real instance of one, assuming it doesn't have too many dependencies.
On the plus side, `HttpRequestHeaders` doesn't have too many dependencies. On the down side, it only has an `internal` constructor. Happily, though, `HttpRequestMessage` can be freely constructed and exposes a `Headers` property which will perform the required construction for you.
Alternatively, you might consider using reflection to create the object despite it only having the `internal` constructor - it's pick your poison time - create an unneeded, disposable object to cleanly create the headers, or start using reflection.
Problem
I have a class `A` that expose a `HttpRequestHeaders` as a property. The class under test is `B`. - `B` is using `A`. - `A` is also a fake class that is used only for unit test. - `A` inherit an interface that impose the definition of the `HttpRequestHeaders` property. So I need to substitute the `HttpRequestHeaders` so that I can test `B` Unfortunately `HttpRequestHeaders` is a sealed class thus it can not be substitute by NSubstitute: Could not load type 'Castle.Proxies.HttpRequestHeadersProxy_2' from assembly 'DynamicProxyGenAssembly2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=a621a9e7e5c32e69' because the parent type is sealed. What would be the general solution to overcome this situation?