Implement rspec TestEnvHelpers:

Allow use of our test environment, with a mocked remote and convenient
methods to write more concise expectations.

  #env, builds and returns a memoized test environment (with mocked
  remote)

  #output, returns env output as a string

  #remote_fs, returns env remote fs

  #expect_execution, setup a remote command execution expectation

spec/spec_helper.rb

@@ -6,6 +6,8 @@ Dir['spec/support/**/*.rb'].map { |e| require e.gsub 'spec/', '' }
 RSpec.configure do |c|
   c.treat_symbols_as_metadata_keys_with_true_values = true
 
+  c.include TestEnvHelpers, :env
+
   c.include NetSSHStoryHelpers, :ssh
   c.before(:each, :ssh) do
     allow(Net::SSH).to receive(:start) { connection }