[test] Add ability to run tests in a Docker container

.dockerignore

+*
+!Gemfile
+!Gemfile.lock
\ No newline at end of file

Dockerfile

+FROM ruby:2.6
+
+RUN apt-get update \
+	&& apt-get install -y sudo golang --no-install-recommends
+RUN apt-get purge --auto-remove -y curl \
+	&& rm -rf /var/lib/apt/lists/*
+
+RUN groupadd -r app && useradd -r -g app -G sudo app \
+    && mkdir -p /home/app && chown -R app:app /home/app
+RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
+
+USER app
+
+# throw errors if Gemfile has been modified since Gemfile.lock
+RUN bundle config --global frozen 1
+
+WORKDIR /home/app/workdir
+
+COPY Gemfile Gemfile.lock ./
+RUN bundle install
+
+ENV LANG C.UTF-8
+ENV GOFLAGS -mod=vendor
+ENV USER app

script/docker

+#!/bin/bash
+# Usage: script/docker [<cucumber-args>]
+set -e
+
+container=hub-test
+workdir=/home/app/workdir
+
+docker build -t "$container" .
+
+docker run -it --rm -v "$PWD":"$workdir" -w "$workdir" "$container" \
+  /bin/bash -c "
+# Enables running WEBrick server (see local_server.rb)
+# https://stackoverflow.com/a/45899937/11687
+cp /etc/hosts /tmp/hosts.new \
+	&& sed -i 's/::1\\tlocalhost/::1/' /tmp/hosts.new \
+	&& sudo cp -f /tmp/hosts.new /etc/hosts || exit 1
+
+go test ./...
+bundle exec cucumber $@
+"
\ No newline at end of file