- Add a `make test-spectron` target
- Install `spectron` and `mocha` (since we don't need to run the tests
inside an Electron instance like in the case of `electron-mocha`)
- Add some example tests
Fixes: https://github.com/resin-io/etcher/issues/1870
Change-Type: patch
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>