I've developed an application using Polymer 1.0. My developer computer is a Mac, and I've not had any problems during development process.
However, when I clone my application on a Windows machine (Windows 10), the tests don't work at all.
Whenever I execute polymer test or wct the command blocks the terminal and never ends.
On MACOS or Linux it works perfectly.
I finally found a workaround.
It seems that there is a bug in Web Component Tester. When it tries to find all the browsers installed on a windows machine it takes ages to locate some of them.
To solve this problem, just adds an environment variable that tells WCT which browsers are installed, so it can skip this step:
LAUNCHPAD_BROWSERS= _{coma delimited list of browsers}_
For instance:
LAUNCHPAD_BROWSERS=chrome,firefox,opera
Once this variable has been set, all the tests execute just like on any other OS.
More information about this feature here