I added some tests for your calculator. Please implement the Calculator ...

...class so all tests would pass.

Read a little about http://www.nuget.org/. Pull my changes and try to build the project. You might have to "Enable NuGet package restore". If yes - google on that.

Also please install NUnit Test adapter in Tools-> Extensions and Updates...

![image](https://f.cloud.github.com/assets/546843/2506908/eb292f32-b3af-11e3-804f-bac132755f60.png)