Merge pull request #931 from mbj/add/world-capture-stdout

Add Mutant::World#capture_stdout

Author: mbj

lib/mutant/config.rb

@@ -29,6 +29,21 @@ class World
     def inspect
       INSPECT
     end
+
+    # Capture stdout of a command
+    #
+    # @param [Array<String>] command
+    #
+    # @return [Either<String,String>]
+    def capture_stdout(command)
+      stdout, status = open3.capture2(*command, binmode: true)
+
+      if status.success?
+        Either::Right.new(stdout)
+      else
+        Either::Left.new("Command #{command} failed!")
+      end
+    end
   end # World
 
   # Standalone configuration of a mutant execution.

spec/unit/mutant/world_spec.rb

@@ -22,4 +22,42 @@ def apply
       expect(apply).to be(apply)
     end
   end
+
+  describe '#capture_stdout' do
+    def apply
+      subject.capture_stdout(command)
+    end
+
+    let(:open3)          { class_double(Open3)              }
+    let(:stdout)         { instance_double(String, :stdout) }
+    let(:subject)        { super().with(open3: open3)       }
+    let(:command)        { %w[foo bar baz]                  }
+
+    let(:process_status) do
+      instance_double(
+        Process::Status,
+        success?: success?
+      )
+    end
+
+    before do
+      allow(open3).to receive_messages(capture2: [stdout, process_status])
+    end
+
+    context 'when process exists successful' do
+      let(:success?) { true }
+
+      it 'returns stdout' do
+        expect(apply).to eql(Mutant::Either::Right.new(stdout))
+      end
+    end
+
+    context 'when process exists unsuccessful' do
+      let(:success?) { false }
+
+      it 'returns stdout' do
+        expect(apply).to eql(Mutant::Either::Left.new("Command #{command.inspect} failed!"))
+      end
+    end
+  end
 end