More test coverage

[karlnorling]

Adding some more tests.

[cv711]

Why don't we run all those tests during CI builds?

[karlnorling]

@cv711 I had issues with downloading and building capnp in circle ci. One have to build it from source and a special version for node 8. And then install the npm capnp lib.

[cv711]

@karlnorling we could run the tests inside the sandbox container we are building no?

[karlnorling]

@cv711 this is a lot more work than I thought - and I'm not sure if updating the baseexec docker image does changes to the built docker image later. I'm also having issues compiling cap'nproto on the alpine distro - it's missing a fair amount of different things.

          echo Installing Capn'Proto for node 8
          apk --no-cache add openssl wget
          apk add build-base
          curl -O https://capnproto.org/capnproto-c++-0.6.1.tar.gz
          tar zxf capnproto-c++-0.6.1.tar.gz
          cd capnproto-c++-0.6.1
          ./configure
          make -j6 check
          sudo make install

Right now it's failing on make -j6 check

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I./src -I./src -DKJ_HEADER_WARNINGS -DCAPNP_HEADER_WARNINGS "-DCAPNP_INCLUDE_DIR=\"/usr/local/include\"" -O2 -DNDEBUG -MT src/kj/mutex.lo -MD -MP -MF src/kj/.deps/mutex.Tpo -c src/kj/mutex.c++  -fPIC -DPIC -o src/kj/.libs/mutex.o
src/kj/mutex.c++:34:25: fatal error: linux/futex.h: No such file or directory
 #include <linux/futex.h>

And I have no idea how to install futex kernel tool on alpine distro.