Rspec test failing against Docker container - ruby

Question

DISCLAIMER: I am new to ruby,rspec etc. I am trying to find a test framework for my docker containers
I have a docker container that runs the aws cli. I have tested this manually and it work, as part of my tests I want to get the AWS version and check it.
I have created this test
it "aws is the correct version" do
expect(aws_version).to include("aws")
end
def aws_version
command("aws --version").stdout
end
When I run it I get which shows the exepected as blank, it looks like it is not running and returning anything
1) Dockerfile aws is the coorect version
Failure/Error: expect(aws_version).to include("aws")
expected "" to include "aws"
# ./tests_spec.rb:37:in `block (2 levels) in <top (required)>'
All my other tests run against the container correctly. I have included both my dockerfile and test_spec below
Dockerfile:
FROM ubuntu:16.04
ENV LAST_UPDATE=09-04-2017
#####################################################################################
# Current version is aws-cli/1.11.83 Python/2.7.12 Linux/4.4.0-75-generic botocore/1.5.46
#####################################################################################
RUN apt-get update && apt-get -y upgrade
RUN apt-get install python-pip -y
RUN pip install --upgrade pip
RUN pip install --upgrade awscli s3cmd python-magic
RUN export PATH=~/.local/bin:$PATH
RUN mkdir /root/.aws
COPY config /root/.aws
#COPY credentials /root/.aws
WORKDIR /root
ENTRYPOINT ["aws"]
CMD ["--version"]
test_spec.rb:
require "docker"
require "serverspec"
describe "Dockerfile" do
before(:all) do
#image = Docker::Image.build_from_dir('.')
set :os, family: :ubuntu
set :backend, :docker
set :docker_image, #image.id
#container = Docker::Container.create(
'Image' => #image.id,
)
#container.start
end
it "installs the right version Name of Ubuntu" do
expect(os_version).to include("xenial")
end
it "installs the right version of Ubuntu" do
expect(os_version).to include("Ubuntu 16.04.2")
end
it "installs required packages" do
expect(package("python-pip")).to be_installed
end
it "aws is the coorect version" do
expect(aws_version).to include("aws")
end
def aws_version
command("aws --version").stdout
end
def os_version
command("cat /etc/lsb-release").stdout
end
after(:all) do
#container.kill
#container.delete(:force => true)
end
end

Answer 1

Pretty simple (but took me a while to spot): for some reason the aws --version command pumps it's output onto stderr rather than stdout. So do this instead:
def aws_version
command("aws --version").stderr
end
Also, it's worth noting that all your container does by default is run the aws --version command and then exits. So as long as your specs run fast enough you'll be okay, but if they don't then they're going to fail randomly.
In your specs I'd override your image's default entrypoint/cmd and put in a simple while true; do sleep 100; done so that it stays alive until your after blocks kills the container.