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/producer/core/actions/echo_spec.rb

@@ -2,8 +2,7 @@ require 'spec_helper'
 
 module Producer::Core
   module Actions
-    describe Echo do
-      let(:env)       { Env.new(output: StringIO.new) }
+    describe Echo, :env do
       let(:text)      { 'hello' }
       subject(:echo)  { Echo.new(env, text) }
 
@@ -12,7 +11,7 @@ module Producer::Core
       describe '#apply' do
         it 'writes the given string to env output with a record separator' do
           echo.apply
-          expect(env.output.string).to eq "hello\n"
+          expect(output).to eq "hello\n"
         end
       end
     end

spec/producer/core/actions/file_writer_spec.rb

@@ -2,8 +2,7 @@ require 'spec_helper'
 
 module Producer::Core
   module Actions
-    describe FileWriter do
-      let(:env)         { Env.new }
+    describe FileWriter, :env do
       let(:path)        { 'some_path' }
       let(:content)     { 'some_content' }
       subject(:writer)  { FileWriter.new(env, path, content) }
@@ -12,7 +11,7 @@ module Producer::Core
 
       describe '#apply' do
         it 'writes content to file on remote filesystem' do
-          expect(writer.fs).to receive(:file_write).with(path, content)
+          expect(remote_fs).to receive(:file_write).with(path, content)
           writer.apply
         end
       end

spec/producer/core/actions/mkdir_spec.rb

@@ -2,8 +2,7 @@ require 'spec_helper'
 
 module Producer::Core
   module Actions
-    describe Mkdir do
-      let(:env)       { Env.new }
+    describe Mkdir, :env do
       let(:path)      { 'some_path' }
       subject(:mkdir) { Mkdir.new(env, path) }
 
@@ -11,7 +10,7 @@ module Producer::Core
 
       describe '#apply' do
         it 'creates directory on remote filesystem' do
-          expect(mkdir.fs).to receive(:mkdir).with(path)
+          expect(remote_fs).to receive(:mkdir).with(path)
           mkdir.apply
         end
       end

spec/producer/core/actions/shell_command_spec.rb

@@ -2,8 +2,7 @@ require 'spec_helper'
 
 module Producer::Core
   module Actions
-    describe ShellCommand do
-      let(:env)           { Env.new(output: StringIO.new) }
+    describe ShellCommand, :env do
       let(:command_args)  { 'hello from remote host' }
       let(:command)       { "echo #{command_args}" }
       subject(:sh)        { ShellCommand.new(env, command) }
@@ -12,14 +11,13 @@ module Producer::Core
 
       describe '#apply' do
         it 'executes the remote command' do
-          expect(sh.remote).to receive(:execute).with(command)
+          expect_execution(command)
           sh.apply
         end
 
         it 'writes the returned output with a record separator' do
-          allow(sh.remote).to receive(:execute) { command_args }
           sh.apply
-          expect(sh.output.string).to eq "#{command_args}\n"
+          expect(output).to eq "#{command_args}\n"
         end
       end
     end