Add a unit test app + example tests

test/main/CMakeLists.txt

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+idf_component_register(SRCS "main.c" INCLUDE_DIRS ".")

test/main/main.c

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+#include <stdio.h>
+#include <string.h>
+#include "unity.h"
+
+static void print_banner(const char* text);
+
+void app_main(void)
+{
+    print_banner("Running tests without [ignore] tag");
+    UNITY_BEGIN();
+    unity_run_tests_by_tag("[ignore]", true);
+    UNITY_END();
+
+    print_banner("Starting interactive test menu");
+    unity_run_menu();
+}
+
+static void print_banner(const char* text)
+{
+    printf("\n#### %s #####\n\n", text);
+}
+