add execute command

lib/foreman/cli.rb

@@ -13,6 +13,13 @@ class Foreman::CLI < Thor
     Foreman::Engine.new(procfile).start
   end
 
+  desc "execute PROCESS [PROCFILE]", "Run an instance of the specified process from PROCFILE"
+
+  def execute(process, procfile="Procfile")
+    error "#{procfile} does not exist." unless procfile_exists?(procfile)
+    Foreman::Engine.new(procfile).execute(process)
+  end
+
   desc "export APP [PROCFILE] [FORMAT]", "Export the app described in PROCFILE as APP to another FORMAT"
 
   def export(app, procfile="Procfile", format="upstart")

spec/foreman/cli_spec.rb

@@ -25,6 +25,27 @@ describe "Foreman::CLI" do
     end
   end
 
+  describe "execute" do
+    describe "with a non-existent Procfile" do
+      it "prints an error" do
+        mock_error(subject, "Procfile does not exist.") do
+          dont_allow.instance_of(Foreman::Engine).start
+          subject.execute("alpha")
+        end
+      end
+    end
+
+    describe "with a Procfile" do
+      before(:each) { write_procfile }
+
+      it "runs successfully" do
+        dont_allow(subject).error
+        mock.instance_of(Foreman::Engine).execute("alpha")
+        subject.execute("alpha")
+      end
+    end
+  end
+
   describe "export" do
     describe "with a non-existent Procfile" do
       it "prints an error" do

spec/foreman/engine_spec.rb

@@ -29,4 +29,12 @@ describe "Foreman::Engine" do
       subject.start
     end
   end
+
+  describe "execute" do
+    it "runs the processes" do
+      write_procfile
+      mock(subject).run(subject.processes["alpha"], false)
+      subject.execute("alpha")
+    end
+  end
 end