Dockerfile
FROM ruby:2.6.3
RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ buster-pgdg main" >> /etc/apt/sources.list.d/pgdg.list \
&& wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
&& apt-get update -qq \
&& apt-get install -y build-essential libpq-dev postgresql-client-11 postgresql-contrib-11
ARG INSTALL_BUNDLER_VERSION=2.0.2
RUN gem install bundler --version=${INSTALL_BUNDLER_VERSION}
ENV BUNDLER_VERSION=${INSTALL_BUNDLER_VERSION}
ENV APP_PATH=/app
RUN mkdir ${APP_PATH}
WORKDIR ${APP_PATH}
ADD . ${APP_PATH}
CMD bundle check || bundle install; bundle exec rspec spec