Add support to store environment variables as facts

This code converts BEAKER_FACTER_* env vars to facts on target machines.
This allows testing variations. While this is similar to tiers, it's not
really the same. For example, a tier can be single node vs multi node,
but those can both be run with multiple versions.

README.md

@@ -90,3 +90,41 @@ It's also possible to skip module installation altogether, giving the module dev
 ```ruby
 configure_beaker(modules: nil)
 ```
+
+## Environment variables to facts
+
+It can be useful to provide facts via environment variables. A possible use is run the test suite with version 1.0 and 1.1. Often it's much easier to run the entire suite with version 1.0 and run it with 1.1 in a complete standalone fashion.
+
+Voxpupuli-acceptance converts all environment variables starting with `BEAKER_FACTER_` and stores them in `/etc/facter/facts.d/voxpupuli-acceptance-env.json` on the target machine. All environment variables are converted to lowercase.
+
+Given following `spec_helper_acceptance.rb` is used:
+
+```ruby
+require 'voxpupuli/acceptance/spec_helper_acceptance'
+
+MANIFEST = <<PUPPET
+class { 'mymodule':
+  version => fact('mymodule_version'),
+}
+PUPPET
+
+configure_beaker do |host|
+  apply_manifest_on(host, MANIFEST, catch_failures: true)
+end
+```
+
+Then it can be tested with:
+```bash
+BEAKER_FACTER_MYMODULE_VERSION=1.0 bundle exec rake beaker
+BEAKER_FACTER_MYMODULE_VERSION=1.1 bundle exec rake beaker
+```
+
+Many CI systems make it easy to build a matrix with this.
+
+If no environment variables are present, the file is removed. It is not possible to store structured facts.
+
+This behavior can be disabled altogether:
+
+```ruby
+configure_beaker(configure_facts_from_env: false)
+```

lib/voxpupuli/acceptance/spec_helper_acceptance.rb

@@ -1,4 +1,31 @@
-def configure_beaker(modules: :metadata, &block)
+ENV_VAR_PREFIX = 'BEAKER_FACTER_'
+FACT_FILE = '/etc/facter/facts.d/voxpupuli-acceptance-env.json'
+
+def beaker_facts_from_env
+  facts = {}
+
+  ENV.each do |var, value|
+    next unless var.start_with?(ENV_VAR_PREFIX)
+
+    fact = var.sub(ENV_VAR_PREFIX, '').downcase
+    facts[fact] = value
+  end
+
+  facts
+end
+
+def write_beaker_facts_on(hosts)
+  beaker_facts = beaker_facts_from_env
+
+  if beaker_facts.any?
+    require 'json'
+    on(hosts, "mkdir -p #{File.dirname(FACT_FILE)} && cat <<VOXPUPULI_BEAKER_ENV_VARS > #{FACT_FILE}\n#{beaker_facts.to_json}\nVOXPUPULI_BEAKER_ENV_VARS")
+  else
+    on(hosts, "rm -f #{FACT_FILE}")
+  end
+end
+
+def configure_beaker(modules: :metadata, configure_facts_from_env: true, &block)
   ENV['PUPPET_INSTALL_TYPE'] ||= 'agent'
   ENV['BEAKER_PUPPET_COLLECTION'] ||= 'puppet6'
   ENV['BEAKER_debug'] ||= 'true'
@@ -33,6 +60,8 @@ def configure_beaker(modules: :metadata, &block)
         Voxpupupli::Acceptance::Fixtures.install_fixture_modules_on(hosts, fixture_modules)
       end
 
+      write_beaker_facts_on(hosts) if configure_facts_from_env
+
       if block
         hosts.each do |host|
           yield host