WIP/PoC: esp_netif UT as a test app

components/unity/include/unity_fixture_extras.h

@@ -0,0 +1,11 @@
+/* IDF-specific additions to "Unity Fixture" */
+#pragma once
+
+/* A shorthand for running one test group from the main function */
+#define UNITY_MAIN(group_) do { \
+    const char* argv[] = { "test", "-v" }; \
+    const int argc = sizeof(argv)/sizeof(argv[0]); \
+    int rc = UnityMain(argc, argv, TEST_ ## group_ ## _GROUP_RUNNER); \
+    printf("\nTests finished, rc=%d\n", rc); \
+    exit(rc); \
+} while(0)