Implement `` condition keyword (shell cmd status)

features/tests/shell_command_status.feature

@@ -0,0 +1,30 @@
+@sshd
+Feature: `` condition keyword
+
+  Scenario: succeeds when remote command execution is a success
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_remote_command do
+        condition { `true` }
+
+        echo 'evaluated'
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must contain "evaluated"
+
+  Scenario: succeeds when remote executable is available
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_remote_command do
+        condition { `false` }
+
+        echo 'evaluated'
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must not contain "evaluated"

lib/producer/core.rb

@@ -21,6 +21,7 @@ require 'producer/core/tests/has_dir'
 require 'producer/core/tests/has_env'
 require 'producer/core/tests/has_executable'
 require 'producer/core/tests/has_file'
+require 'producer/core/tests/shell_command_status'
 
 require 'producer/core/cli'
 require 'producer/core/condition'

lib/producer/core/condition/dsl.rb

@@ -13,6 +13,7 @@ module Producer
           end
         end
 
+        define_test :`,               Tests::ShellCommandStatus
         define_test :file_contains,   Tests::FileContains
         define_test :has_env,         Tests::HasEnv
         define_test :has_executable,  Tests::HasExecutable

lib/producer/core/tests/shell_command_status.rb

@@ -0,0 +1,18 @@
+module Producer
+  module Core
+    module Tests
+      class ShellCommandStatus < Test
+        def verify
+          remote.execute(command)
+          true
+        rescue RemoteCommandExecutionError
+          false
+        end
+
+        def command
+          arguments.first
+        end
+      end
+    end
+  end
+end

spec/producer/core/condition/dsl_spec.rb

@@ -8,6 +8,7 @@ module Producer::Core
       subject(:dsl) { DSL.new(env, &block) }
 
       %w[
+        `
         file_contains
         has_dir
         has_env

spec/producer/core/tests/shell_command_status_spec.rb

@@ -0,0 +1,34 @@
+require 'spec_helper'
+
+module Producer::Core
+  module Tests
+    describe ShellCommandStatus, :env do
+      let(:command)   { 'true' }
+      subject(:test)  { described_class.new(env, command) }
+
+      it_behaves_like 'test'
+
+      describe '#verify' do
+        context 'command return status is 0' do
+          it 'returns true' do
+            expect(test.verify).to be true
+          end
+        end
+
+        context 'command return status is not 0' do
+          let(:command) { 'false' }
+
+          it 'returns false' do
+            expect(test.verify).to be false
+          end
+        end
+      end
+
+      describe '#command' do
+        it 'returns the first argument' do
+          expect(test.command).to eq command
+        end
+      end
+    end
+  end
+end