Implement `has_file' condition keyword

spec/producer/core/tests/has_file_spec.rb

@@ -0,0 +1,28 @@
+require 'spec_helper'
+
+module Producer::Core
+  describe Tests::HasFile do
+    let(:env)           { Env.new }
+    let(:filepath)      { 'some_file' }
+    subject(:has_file)  { Tests::HasFile.new(env, filepath) }
+
+    it 'is a kind of test' do
+      expect(has_file).to be_a Test
+    end
+
+    describe '#success?', :ssh do
+      before { sftp_story }
+
+      it 'delegates the call on remote FS' do
+        expect(env.remote.fs).to receive(:has_file?).with(filepath)
+        has_file.success?
+      end
+
+      it 'returns the file existence' do
+        existence = double('existence')
+        allow(env.remote.fs).to receive(:has_file?) { existence }
+        expect(has_file.success?).to be existence
+      end
+    end
+  end
+end