MutatingStringsBrainTeaser

To quote Randall Munroe

There's a certain type of brain that's easily disabled. If you show it an interesting problem, it involuntarily drops everything else to work on it

This is a simple brain teaser in C# that asks you to simply mutate a string. There are two unit tests that each make a couple assertions on a local string constant.

Rules

1. The only changes that may be made to Tests.cs should be within the CauseIdentityCrisis methods.
2. No pre/post build steps. This can be done with only C# code.
3. No IL manipulation.
4. You are free to make any modifications outside the Tests.cs file that you see fit (hint, none are required, but creative solutions are always welcome)

How about some hints?

Hint 1

Hint 2

Solution

Though I recommend thinking on it rather than jumping straight to the solution. For those who have to know, here it is. You can see the full solution on the "solution" branch. (provided by @savbace).

But Why?

Because brain teasers are fun and I love C#. As a professional developer I love learning the details of how my favorite language and its compiler work. I do not recommend that anyone write code like this in a production application. This type of code is best left to brain teasers.