Refactor actions specs with shared examples

spec/producer/core/actions/echo_spec.rb

@@ -7,6 +7,8 @@ module Producer::Core
       let(:text)      { 'hello' }
       subject(:echo)  { Echo.new(env, text) }
 
+      it_behaves_like 'action'
+
       describe '#apply' do
         it 'writes the given string to env output with a record separator' do
           echo.apply

spec/producer/core/actions/file_writer_spec.rb

@@ -8,6 +8,8 @@ module Producer::Core
       let(:content)     { 'some_content' }
       subject(:writer)  { FileWriter.new(env, path, content) }
 
+      it_behaves_like 'action'
+
       describe '#apply' do
         it 'writes content to file on remote filesystem' do
           expect(writer.fs).to receive(:file_write).with(path, content)

spec/producer/core/actions/mkdir_spec.rb

@@ -7,6 +7,8 @@ module Producer::Core
       let(:path)      { 'some_path' }
       subject(:mkdir) { Mkdir.new(env, path) }
 
+      it_behaves_like 'action'
+
       describe '#apply' do
         it 'creates directory on remote filesystem' do
           expect(mkdir.fs).to receive(:mkdir).with(path)

spec/producer/core/actions/shell_command_spec.rb

@@ -8,6 +8,8 @@ module Producer::Core
       let(:command)       { "echo #{command_args}" }
       subject(:sh)        { ShellCommand.new(env, command) }
 
+      it_behaves_like 'action'
+
       describe '#apply' do
         it 'executes the remote command' do
           expect(sh.remote).to receive(:execute).with(command)