Refactor the test canvas/window usage to be more real

You can choose a re-usable window if you want,
or create an individual one for a single test - which you should close

app.go

@@ -35,9 +35,8 @@ func (app *fyneApp) applyTheme(Settings) {
 		switch themed := content.(type) {
 		case ThemedObject:
 			themed.ApplyTheme()
+			window.Canvas().Refresh(content)
 		}
-
-		window.Canvas().Refresh(content)
 	}
 }
 

test/testcanvas.go

@@ -4,11 +4,6 @@ import "github.com/fyne-io/fyne"
 
 var dummyCanvas fyne.Canvas
 
-// Canvas returns an un-rendered canvas that is used for behavioural testing
-func Canvas() fyne.Canvas {
-	return dummyCanvas
-}
-
 type testCanvas struct {
 	content fyne.CanvasObject
 	focused fyne.FocusableObject
@@ -51,10 +46,15 @@ func (c *testCanvas) SetScale(float32) {
 func (c *testCanvas) SetOnKeyDown(func(*fyne.KeyEvent)) {
 }
 
+// NewTestCanvas returns a single use in-memory canvas used for testing
+func NewTestCanvas() fyne.Canvas {
+	return &testCanvas{}
+}
+
 // GetTestCanvas returns a reusable in-memory canvas used for testing
 func GetTestCanvas() fyne.Canvas {
 	if dummyCanvas == nil {
-		dummyCanvas = &testCanvas{}
+		dummyCanvas = NewTestCanvas()
 	}
 
 	return dummyCanvas

test/testdriver.go

@@ -6,7 +6,7 @@ type testDriver struct {
 }
 
 func (d *testDriver) CreateWindow(string) fyne.Window {
-	return NewTestWindow()
+	return NewTestWindow(nil)
 }
 
 func (d *testDriver) AllWindows() []fyne.Window {
@@ -25,7 +25,7 @@ func (d *testDriver) Quit() {
 func NewTestDriver() fyne.Driver {
 	driver := new(testDriver)
 	// make a single dummy window for rendering tests
-	NewTestWindow()
+	NewTestWindow(nil)
 
 	return driver
 }

test/testwindow.go

@@ -5,6 +5,8 @@ import "github.com/fyne-io/fyne"
 type testWindow struct {
 	title      string
 	fullscreen bool
+
+	canvas fyne.Canvas
 }
 
 var windows = make([]fyne.Window, 0)
@@ -29,7 +31,17 @@ func (w *testWindow) Show() {}
 
 func (w *testWindow) Hide() {}
 
-func (w *testWindow) Close() {}
+func (w *testWindow) Close() {
+	i := 0
+	for _, window := range windows {
+		if window == w {
+			break
+		}
+		i++
+	}
+
+	windows = append(windows[:i], windows[i+1:]...)
+}
 
 func (w *testWindow) Content() fyne.CanvasObject {
 	return w.Canvas().Content()
@@ -40,13 +52,15 @@ func (w *testWindow) SetContent(obj fyne.CanvasObject) {
 }
 
 func (w *testWindow) Canvas() fyne.Canvas {
-	return GetTestCanvas()
+	return w.canvas
 }
 
 // NewTestWindow creates and registers a new window for test purposes
-func NewTestWindow() fyne.Window {
-	window := &testWindow{}
-	windows = append(windows, window)
+func NewTestWindow(content fyne.CanvasObject) fyne.Window {
+	canvas := NewTestCanvas()
+	canvas.SetContent(content)
+	window := &testWindow{canvas: canvas}
 
+	windows = append(windows, window)
 	return window
 }

widget/entry_test.go

@@ -64,7 +64,7 @@ func TestEntryFocus(t *testing.T) {
 
 func TestEntryWindowFocus(t *testing.T) {
 	entry := NewEntry()
-	canvas := test.Canvas()
+	canvas := test.GetTestCanvas()
 
 	canvas.Focus(entry)
 	assert.True(t, entry.Focused())

widget/widget_test.go

@@ -8,30 +8,48 @@ import "github.com/stretchr/testify/assert"
 import "github.com/fyne-io/fyne"
 import "github.com/fyne-io/fyne/test"
 
-var applied = make(chan bool)
-
 type myWidget struct {
 	baseWidget
+
+	applied chan bool
 }
 
 func (m *myWidget) ApplyTheme() {
-	applied <- true
+	m.applied <- true
+	close(m.applied)
 }
 
 func TestApplyThemeCalled(t *testing.T) {
-	widget := &myWidget{}
-
-	app := test.NewApp()
-	window := app.NewWindow("Testing")
-	window.SetContent(widget)
+	widget := &myWidget{applied: make(chan bool)}
 
+	window := test.NewTestWindow(widget)
 	fyne.GetSettings().SetTheme("light")
 
 	func() {
 		select {
-		case <-applied:
+		case <-widget.applied:
 		case <-time.After(1 * time.Second):
 			assert.Fail(t, "Timed out waiting for theme apply")
 		}
 	}()
+
+	window.Close()
+}
+
+func TestAppplyThemeCalledChild(t *testing.T) {
+	child := &myWidget{applied: make(chan bool)}
+	parent := NewList(child)
+
+	window := test.NewTestWindow(parent)
+	fyne.GetSettings().SetTheme("light")
+
+	func() {
+		select {
+		case <-child.applied:
+		case <-time.After(1 * time.Second):
+			assert.Fail(t, "Timed out waiting for child theme apply")
+		}
+	}()
+
+	window.Close()
 }