The integration tests depend on having a DNS server that resolves
"localhost", which is unfortunate but currently unavoidable given
glibc's limitations ($HOSTALIASES only works on DNS-level aliases, and
does not do lookups in /etc/hosts).
Even under docker, this makes the tests depend on the DNS server, and
whether it resolves localhost or not.
In order to make the docker tests more hermetic and isolated from the
environment, this patch introduces a docker entrypoint that, within the
container, will launch minidns and override /etc/resolv.conf to use it.
This guarantees that the tests will be able to resolve localhost, and
also avoid accidental reliance on external DNS zones.
Docker creates intermediate layers on each command (for most commands),
but the COPY was invalidating them too early, every time it runs it was
generating a different layer.
This patch moves the COPY down to the bottom, and adds a bit more
organization to the commands below.
This patch adds DKIM signing using https://github.com/driusan/dkim tools
to the example hook.
It also adds an optional integration test to exercise signing and
verification, and corresponding documentation.
This patch adds a new test, which verifies the TLS tracking.
Because we need to simulate SPF records, and Go does not support fully
intercepting DNS lookups yet, this test relies on dnsmasq to provide a
DNS resolver.
In the future, once Go supports DNS lookup interception, we can get rid
of this additional dependency.
This patch adds a Docker configuration file, to build an image that can
run the integration and stress tests.
It might be used for configuring automated testing infrastructure in
subsequent patches.
