Explicitly check whether /dev/ptyvf is busy or not.

lib/bwoken/script.rb

@@ -47,9 +47,22 @@ def device_flag
       simulator ? '' : "-w #{Bwoken::Device.uuid}"
     end
 
+    # unix_instruments will try to open /dev/ptyvf
+    def check_ptyvf!
+      ptyvf_fd = IO.sysopen('/dev/ptyvf', 'r')
+      ptyvf_io = IO.new(ptyvf_fd, 'r')
+    rescue Errno::EBUSY => e
+      # TODO: log error here
+      raise
+    ensure
+      ptyvf_io.close if ptyvf_io
+    end
+
     def run
       formatter.before_script_run path
 
+      check_ptyvf!
+
       Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|
         exit_status = formatter.format stdout
         raise ScriptFailedError.new('Test Script Failed') unless exit_status == 0

spec/lib/bwoken/script_spec.rb

@@ -15,6 +15,7 @@ class Simulator; end
   describe '#run' do
     let(:exit_status) { 0 }
     before do
+      IO.stub(:sysopen).and_return(STDOUT.fcntl(Fcntl::F_DUPFD))
       subject.formatter.stub(:format).and_return(exit_status)
       subject.formatter.stub(:before_script_run)
     end
@@ -132,4 +133,12 @@ class Simulator; end
     end
   end
 
+  describe "#check_ptyvf!" do
+    it "raises an exception when busy" do
+      subject.formatter.stub(:before_script_run)
+      IO.should_receive(:sysopen).with('/dev/ptyvf', 'r').and_raise('busy!')
+      expect { subject.run }.to raise_error RuntimeError, "busy!"
+    end
+  end
+
 end