Index: uspace/lib/ui/test/ui.c
===================================================================
--- uspace/lib/ui/test/ui.c	(revision c632c969ffb9871f32ae6c135490d77fb8a4db87)
+++ uspace/lib/ui/test/ui.c	(revision 7ca721557bbbab9db7f7e937549e3e6bed609586)
@@ -1,4 +1,4 @@
 /*
- * Copyright (c) 2020 Jiri Svoboda
+ * Copyright (c) 2022 Jiri Svoboda
  * All rights reserved.
  *
@@ -169,3 +169,19 @@
 }
 
+/** ui_lock(), ui_unlock() */
+PCUT_TEST(lock_unlock)
+{
+	ui_t *ui = NULL;
+	errno_t rc;
+
+	rc = ui_create_disp((display_t *)(-1), &ui);
+	PCUT_ASSERT_ERRNO_VAL(EOK, rc);
+	PCUT_ASSERT_NOT_NULL(ui);
+
+	ui_lock(ui);
+	ui_unlock(ui);
+
+	ui_destroy(ui);
+}
+
 PCUT_EXPORT(ui);