tests: provide unittests for internal NIB functions

tests/unittests/tests-gnrc_ipv6_nib/Makefile

+include $(RIOTBASE)/Makefile.base

tests/unittests/tests-gnrc_ipv6_nib/Makefile.include

+USEMODULE += gnrc_ipv6_nib
+
+CFLAGS += -DGNRC_IPV6_NIB_NUMOF=16
+CFLAGS += -DGNRC_IPV6_NIB_DEFAULT_ROUTER_NUMOF=4
+
+INCLUDES += -I$(RIOTBASE)/sys/net/gnrc/network_layer/ipv6/nib

tests/unittests/tests-gnrc_ipv6_nib/tests-gnrc_ipv6_nib.c

+/*
+ * Copyright (C) 2017 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#include "tests-gnrc_ipv6_nib.h"
+
+void tests_gnrc_ipv6_nib(void)
+{
+    TESTS_RUN(tests_gnrc_ipv6_nib_internal_tests());
+}

tests/unittests/tests-gnrc_ipv6_nib/tests-gnrc_ipv6_nib.h

+/*
+ * Copyright (C) 2017 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @addtogroup  unittests
+ * @{
+ *
+ * @file
+ * @brief       Unittests for the ``gnrc_ipv6_nib`` module
+ *
+ * @author      Martine Lenders <m.lenders@fu-berlin.de>
+ */
+#ifndef TESTS_GNRC_IPV6_NIB_H
+#define TESTS_GNRC_IPV6_NIB_H
+
+#include "embUnit.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   The entry point of this test suite.
+ */
+void tests_gnrc_ipv6_nib(void);
+
+/**
+ * @brief   Generates tests for internal layer
+ *
+ * @return  embUnit tests if successful, NULL if not.
+ */
+Test *tests_gnrc_ipv6_nib_internal_tests(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* TESTS_GNRC_IPV6_NIB_H */
+/** @} */