Before using Niv, we were following channels meaning we can not
reproduce CI jobs easily.
In this change, we use Niv to pin these dependencies. We are also
addding a tests/default.nix to be able to run these tests locally.
For instance, to run the test extern.nix on the nixpkgs-19.09 release:
nix-build tests/default.nix -A extern.nixpkgs_19_09
Fixes#178
Their CI environment currently doesn't have KVM. This commit should be
reverted when/if they do, for much better CI speed.
You can still run tests locally on your KVM-enabled machine as documented
on the wiki.
Workaround on GitLab is several pieces (injected through .gitlab-ci.yml):
- Make a /dev/kvm file so that nix thinks we have "kvm" system feature
and proceeds with executing the tests.
- Inject a QEMU package that replaces qemu-kvm with a full emulator.
- Monkey-patch the test script to wait longer for the VM to boot, since
it's slow on full emulation. 1200 seconds, double the previous value.
The patch method is not bulletproof, but better than maintaining forks of
nixpkgs.
- Set systemd's DefaultTimeoutStartSec=15min, so nix's "backdoor" test
service doesn't time out on the slow boot.
