I’m currently going through the process creating unit tests for Griddle and thought it would be good to document the steps I took to get Jest up and running. I did not find it as simple as typing npm install -g jest-cli, however it was not too bad.

My primary machine is running Windows 8 — these steps may be a bit different if you’re on Mac / Linux.

1. Install Python - Install version 2.7 of Python and add it to your path or create a PYTHONPATH environment variable.
2. Install Visual Studio (Express Edition is Fine) - Thankfully, this step was not required for me as I already use Visual Studio. We will need this for some of modules that are compiled when we are installing Jest. (Express editions available here — get one of the versions that has C++)
3. Set Visual Studio Version Flags - this step tripped me up a bit at first. We need to tell node-gyp (something that is used for compiling addons) what version of Visual Studio we want to compile with. You can do this either through an environment variable GYP_MSVS_VERSION or the command line option --msvs_version. My environment variable looks a bit like this GYP_MSVS_VERSION=2013 but if you are using Express, I think you have to say GYP_MSVS_VERSION=2013e
4. Install Jest-CLI - Now you can run the command on the Jest docs site npm install jest-cli --save-dev

At this point you should be ready to run Jest, however, I experienced some further trouble on Windows against React components. In the react example, the package.json contains "unmockedModulePathPatterns": ["<rootDir>/node_modules/react"] which is basically stating that we don’t want to mock React when running our tests. Unfortunately, it seemed like we need to change this path to just "unmockedModulePathPatterns": ["react"] in order for the test to run successfully (again on Windows — seems fine on other OS). See this GitHub issue for more on that.

For more reading on installing Jest’s requirements see:

• http://www.steveworkman.com/node-js/2012/installing-jsdom-on-windows/
• https://github.com/atom/atom/issues/2435