Isolate test state and paint full frame

main.go

@@ -1655,6 +1655,9 @@ func (u *ui) noteCurrentVaultPath() {
 }
 
 func (u *ui) layout(gtx layout.Context) layout.Dimensions {
+	// Clear the full frame explicitly so mobile surfaces don't start from an
+	// unpainted black buffer before nested background widgets run.
+	paint.Fill(gtx.Ops, bgColor)
 	u.syncHostedAPI()
 	u.filter()
 	u.processShortcuts(gtx)

main_test.go

@@ -30,6 +30,20 @@ import (
 	"git.julianfamily.org/keepassgo/webdav"
 )
 
+func TestMain(m *testing.M) {
+	stateDir, err := os.MkdirTemp("", "keepassgo-test-state-")
+	if err != nil {
+		panic(err)
+	}
+	if err := os.Setenv("KEEPASSGO_STATE_DIR", stateDir); err != nil {
+		_ = os.RemoveAll(stateDir)
+		panic(err)
+	}
+	code := m.Run()
+	_ = os.RemoveAll(stateDir)
+	os.Exit(code)
+}
+
 func TestUIFiltersUsingVaultModelPathsAndSearch(t *testing.T) {
 	t.Parallel()