Mock out window creation in test

platforms/opencv/test_helper.go

@@ -16,3 +16,11 @@ func (c *testCapture) RetrieveFrame(i int) *cv.IplImage {
 func (c *testCapture) GrabFrame() bool {
 	return true
 }
+
+type window interface {
+	ShowImage(*cv.IplImage)
+}
+
+type testWindow struct{}
+
+func (w *testWindow) ShowImage(i *cv.IplImage) { return }

platforms/opencv/window_driver.go

@@ -7,7 +7,8 @@ import (
 
 type WindowDriver struct {
 	gobot.Driver
-	window *cv.Window
+	window window
+	start  func(*WindowDriver)
 }
 
 func NewWindowDriver(name string) *WindowDriver {
@@ -16,12 +17,15 @@ func NewWindowDriver(name string) *WindowDriver {
 			name,
 			"WindowDriver",
 		),
+		start: func(w *WindowDriver) {
+			w.window = cv.NewWindow(w.Name(), cv.CV_WINDOW_NORMAL)
+		},
 	}
 }
 
 func (w *WindowDriver) Start() bool {
 	cv.StartWindowThread()
-	w.window = cv.NewWindow(w.Name(), cv.CV_WINDOW_NORMAL)
+	w.start(w)
 	return true
 }
 

platforms/opencv/window_driver_test.go

@@ -10,7 +10,11 @@ import (
 )
 
 func initTestWindowDriver() *WindowDriver {
-	return NewWindowDriver("bot")
+	d := NewWindowDriver("bot")
+	d.start = func(w *WindowDriver) {
+		w.window = &testWindow{}
+	}
+	return d
 }
 
 func TestWindowDriverStart(t *testing.T) {