Implement dry run mode

features/cli/dry_run.feature

@@ -0,0 +1,11 @@
+Feature: CLI dry run option
+
+  Scenario: perfoms a trial run without applying actions
+    Given a recipe with:
+      """
+      task :say_hello do
+        echo 'hello'
+      end
+      """
+    When I successfully execute the recipe with option -n
+    Then the output must not contain "hello"

features/cli/usage.feature

@@ -5,5 +5,5 @@ Feature: CLI usage
     Then the exit status must be 64
     And the output must contain exactly:
       """
-      Usage: producer [-v] recipe_file
+      Usage: producer [-v] [-n] recipe_file
       """

lib/producer/core/cli.rb

@@ -3,7 +3,7 @@ module Producer
     class CLI
       ArgumentError = Class.new(::ArgumentError)
 
-      USAGE = "Usage: #{File.basename $0} [-v] recipe_file"
+      USAGE = "Usage: #{File.basename $0} [-v] [-n] recipe_file"
 
       EX_USAGE = 64
 
@@ -33,6 +33,8 @@ module Producer
           case e
           when '-v'
             env.log_level = Logger::INFO
+          when '-n'
+            env.dry_run = true
           else
             m << e
           end

lib/producer/core/env.rb

@@ -2,13 +2,14 @@ module Producer
   module Core
     class Env
       attr_reader   :input, :output, :registry, :logger
-      attr_accessor :target
+      attr_accessor :target, :dry_run
 
       def initialize(input: $stdin, output: $stdout, remote: nil, registry: {})
         @input    = input
         @output   = output
         @registry = registry
         @remote   = remote
+        @dry_run  = false
       end
 
       def remote
@@ -43,6 +44,10 @@ module Producer
       def log_level=(level)
         logger.level = level
       end
+
+      def dry_run?
+        @dry_run
+      end
     end
   end
 end

lib/producer/core/worker.rb

@@ -17,7 +17,7 @@ module Producer
           env.log ' condition: met'
           task.actions.each do |e|
             env.log " action: #{e} applying"
-            e.apply
+            e.apply unless env.dry_run?
           end
         else
           env.log ' condition: NOT met'

spec/producer/core/cli_spec.rb

@@ -6,7 +6,8 @@ module Producer::Core
     include FixturesHelpers
 
     let(:recipe_file) { fixture_path_for 'recipes/some_recipe.rb' }
-    let(:arguments)   { [recipe_file] }
+    let(:options)     { [] }
+    let(:arguments)   { [*options, recipe_file] }
     let(:stdout)      { StringIO.new }
 
     subject(:cli)     { CLI.new(arguments, stdout: stdout) }
@@ -36,7 +37,7 @@ module Producer::Core
 
       context 'when an argument error is raised' do
         before do
-          allow(CLI).to receive(:new) { cli }
+          allow(described_class).to receive(:new) { cli }
           allow(cli).to receive(:parse_arguments!)
             .and_raise described_class::ArgumentError
         end
@@ -60,7 +61,7 @@ module Producer::Core
       end
 
       context 'without options' do
-        subject(:cli) { CLI.new(arguments) }
+        subject(:cli) { described_class.new(arguments) }
 
         it 'assigns $stdout as the default standard output' do
           expect(cli.stdout).to be $stdout
@@ -82,7 +83,7 @@ module Producer::Core
 
     describe '#parse_arguments!' do
       context 'with options' do
-        let(:arguments) { ['-v', recipe_file] }
+        let(:options) { %w[-v] }
 
         before { cli.parse_arguments! }
 
@@ -95,6 +96,14 @@ module Producer::Core
             expect(cli.env.log_level).to eq Logger::INFO
           end
         end
+
+        context 'dry run' do
+          let(:options) { %w[-n] }
+
+          it 'enables env dry run' do
+            expect(cli.env).to be_dry_run
+          end
+        end
       end
 
       context 'without arguments' do

spec/producer/core/env_spec.rb

@@ -18,6 +18,10 @@ module Producer::Core
         expect(env.registry).to be_empty
       end
 
+      it 'assigns dry run as false' do
+        expect(env.dry_run).to be false
+      end
+
       context 'when output is not given as argument' do
         subject(:env) { Env.new }
 
@@ -133,5 +137,13 @@ module Producer::Core
         expect(env.logger.level).to eq Logger::DEBUG
       end
     end
+
+    describe '#dry_run?' do
+      before { env.dry_run = true }
+
+      it 'returns true when dry run is enabled' do
+        expect(env.dry_run?).to be true
+      end
+    end
   end
 end

spec/producer/core/worker_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 
 module Producer::Core
   describe Worker do
-    let(:env)         { double 'env', log: nil }
+    let(:env)         { double 'env', log: nil, dry_run?: false }
     subject(:worker)  { described_class.new(env) }
 
     describe '#process' do
@@ -37,6 +37,15 @@ module Producer::Core
           expect(env).to receive(:log).with /\A action: echo/
           worker.process_task task
         end
+
+        context 'when dry run is enabled' do
+          before { allow(env).to receive(:dry_run?) { true } }
+
+          it 'does not apply the actions' do
+            expect(action).not_to receive :apply
+            worker.process_task task
+          end
+        end
       end
 
       context 'when task condition is not met' do