Feature/zephyr ztest (#118)

* Leverage (older) embedded unit tests into external unit tests build upon copy of Zephyr's ztest library and CMake.

* Expand top-level CMake build to run external unit tests.

* Expand Zephyr module extension to run external unit tests via west or sanitycheck.

Co-authored-by: Gregory Shue <gregory.shue@legrand.us>

test/bacnet/memcopy/src/main.c

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2020 Legrand North America, LLC.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+/* @file
+ * @brief test BACnet integer encode/decode APIs
+ */
+
+#include <ztest.h>
+#include <bacnet/memcopy.h>
+
+/**
+ * @addtogroup bacnet_tests
+ * @{
+ */
+
+/**
+ * @brief Test
+ */
+static void test_memcopy(void)
+{
+    char *data1 = "Joshua";
+    char *data2 = "Anna";
+    char buffer[480] = "";
+    char big_buffer[480] = "";
+    size_t len = 0;
+
+    len = memcopy(&buffer[0], &data1[0], 0, sizeof(data1), sizeof(buffer));
+    zassert_equal(len, sizeof(data1), NULL);
+    zassert_equal(memcmp(&buffer[0], &data1[0], len), 0, NULL);
+    len = memcopy(&buffer[0], &data2[0], len, sizeof(data2), sizeof(buffer));
+    zassert_equal(len, sizeof(data2), NULL);
+    len = memcopy(
+        &buffer[0], &big_buffer[0], 1, sizeof(big_buffer), sizeof(buffer));
+    zassert_equal(len, 0, NULL);
+}
+/**
+ * @}
+ */
+
+
+void test_main(void)
+{
+    ztest_test_suite(memcopy_tests,
+     ztest_unit_test(test_memcopy)
+     );
+
+    ztest_run_test_suite(memcopy_tests);
+}