@@ 35,10 35,10 @@ func eventLoop(s Screen, evch chan Event
 
 func TestMouseEvents(t *testing.T) {
 
-	WithScreen(t, "", func(s SimulationScreen) {
+	WithScreen(t, "", func(s Screen) {
 
 		s.EnableMouse()
-		s.InjectMouse(4, 9, Button1, ModCtrl)
+		s.(*SimScreen).InjectMouse(4, 9, Button1, ModCtrl)
 		evch := make(chan Event)
 		go eventLoop(s, evch)
 

          

@@ 20,7 20,7 @@ import (
 
 func TestCanDisplay(t *testing.T) {
 
-	WithScreen(t, "UTF-8", func(s SimulationScreen) {
+	WithScreen(t, "UTF-8", func(s Screen) {
 		assertEqual("utf8 1", s.CharacterSet(), "UTF-8", t)
 		assertEqual("utf8 2", s.CanDisplay('a', true), true, t)
 		assertEqual("utf8 3", s.CanDisplay(RuneHLine, true), true, t)

          
@@ 28,7 28,7 @@ func TestCanDisplay(t *testing.T) {
 		assertEqual("utf8 5", s.CanDisplay('⌀', false), true, t)
 	})()
 
-	WithScreen(t, "US-ASCII", func(s SimulationScreen) {
+	WithScreen(t, "US-ASCII", func(s Screen) {
 		assertEqual("ascii 1", s.CharacterSet(), "US-ASCII", t)
 		assertEqual("ascii 2", s.CanDisplay('a', true), true, t)
 		assertEqual("ascii 3", s.CanDisplay(RuneHLine, true), true, t)

          
@@ 40,7 40,7 @@ func TestCanDisplay(t *testing.T) {
 
 func TestRegisterFallback(t *testing.T) {
 
-	WithScreen(t, "US-ASCII", func(s SimulationScreen) {
+	WithScreen(t, "US-ASCII", func(s Screen) {
 		assertEqual("ascii 1", s.CharacterSet(), "US-ASCII", t)
 		s.RegisterRuneFallback('⌀', "o")
 		assertEqual("registered false", s.CanDisplay('⌀', false), false, t)

          
@@ 54,7 54,7 @@ func TestRegisterFallback(t *testing.T) 
 
 func TestUnregisterFallback(t *testing.T) {
 
-	WithScreen(t, "US-ASCII", func(s SimulationScreen) {
+	WithScreen(t, "US-ASCII", func(s Screen) {
 		assertEqual("ascii 1", s.CharacterSet(), "US-ASCII", t)
 
 		assertEqual("registered", s.CanDisplay(RuneHLine, true), true, t)

          

@@ 18,44 18,7 @@ import (
 	"testing"
 )
 
-// SimulationScreen represents a screen simulation.  This is intended to
-// be a superset of normal Screens, but also adds some important interfaces
-// for testing.
-type SimulationScreen interface {
-	// InjectKeyBytes injects a stream of bytes corresponding to
-	// the native encoding (see charset).  It turns true if the entire
-	// set of bytes were processed and delivered as KeyEvents, false
-	// if any bytes were not fully understood.  Any bytes that are not
-	// fully converted are discarded.
-	InjectKeyBytes(buf []byte) bool
-
-	// InjectKey injects a key event.  The rune is a UTF-8 rune, post
-	// any translation.
-	InjectKey(key Key, r rune, mod ModMask)
-
-	// InjectMouse injects a mouse event.
-	InjectMouse(x, y int, buttons ButtonMask, mod ModMask)
-
-	// SetSize resizes the underlying physical screen.  It also causes
-	// a resize event to be injected during the next Show() or Sync().
-	// A new physical contents array will be allocated (with data from
-	// the old copied), so any prior value obtained with GetContents
-	// won't be used anymore
-	SetSize(width, height int)
-
-	// GetContents returns screen contents as an array of
-	// cells, along with the physical width & height.   Note that the
-	// physical contents will be used until the next time SetSize()
-	// is called.
-	GetContents() (cells []SimCell, width int, height int)
-
-	// GetCursor returns the cursor details.
-	GetCursor() (x int, y int, visible bool)
-
-	Screen
-}
-
-func WithScreen(t *testing.T, charset string, fn func(s SimulationScreen)) func() {
+func WithScreen(t *testing.T, charset string, fn func(s Screen)) func() {
 	return func() {
 		s, e := NewSimScreen(charset)
 		assertNotEqual("sim screen", s, nil, t)

          
@@ 67,7 30,7 @@ func WithScreen(t *testing.T, charset st
 
 func TestInitScreen(t *testing.T) {
 
-	WithScreen(t, "", func(s SimulationScreen) {
+	WithScreen(t, "", func(s Screen) {
 		x, y := s.Size()
 		assertEqual("x", x, 80, t)
 		assertEqual("y", y, 25, t)

          
@@ 75,7 38,7 @@ func TestInitScreen(t *testing.T) {
 		assertEqual("character set", s.CharacterSet(), "UTF-8", t)
 
 		//Backing size is correct
-		b, x, y := s.GetContents()
+		b, x, y := s.(*SimScreen).GetContents()
 		assertNotEqual("data", b, nil, t)
 		assertEqual("x", x, 80, t)
 		assertEqual("y", y, 25, t)

          
@@ 85,10 48,10 @@ func TestInitScreen(t *testing.T) {
 }
 
 func TestClearScreen(t *testing.T) {
-	WithScreen(t, "", func(s SimulationScreen) {
+	WithScreen(t, "", func(s Screen) {
 
 		s.Clear()
-		b, x, y := s.GetContents()
+		b, x, y := s.(*SimScreen).GetContents()
 		assertNotEqual("data", b, nil, t)
 		assertEqual("x", x, 80, t)
 		assertEqual("y", y, 25, t)

          
@@ 122,10 85,10 @@ func TestClearScreen(t *testing.T) {
 }
 
 func TestSetCell(t *testing.T) {
-	WithScreen(t, "", func(s SimulationScreen) {
+	WithScreen(t, "", func(s Screen) {
 		st := StyleDefault.Background(ColorRed).Blink(true)
 		s.SetContent(2, 5, '@', nil, st)
-		b, x, y := s.GetContents()
+		b, x, y := s.(*SimScreen).GetContents()
 		assertEqual("x", x, 80, t)
 		assertEqual("y", y, 25, t)
 		assertEqual("backing len", len(b), x*y, t)

          
@@ 142,15 105,15 @@ func TestSetCell(t *testing.T) {
 }
 
 func TestResize(t *testing.T) {
-	WithScreen(t, "", func(s SimulationScreen) {
+	WithScreen(t, "", func(s Screen) {
 		st := StyleDefault.Background(ColorYellow).Underline(true)
 		s.SetContent(2, 5, '&', nil, st)
-		b, _, _ := s.GetContents()
+		ss := s.(*SimScreen)
+		b, _, _ := ss.GetContents()
 		s.Show()
-
-		s.SetSize(30, 10)
+		ss.SetSize(30, 10)
 		s.Show()
-		b2, x2, y2 := s.GetContents()
+		b2, x2, y2 := ss.GetContents()
 		_ = b2
 		// todo			So(b2, ShouldNotEqual, b)
 		assertEqual("x", x2, 30, t)

          

@@ 69,6 69,8 @@ type SimCell struct {
 	Runes []rune
 }
 
+var _ Screen = new(SimScreen)
+
 type SimScreen struct {
 	physw int
 	physh int