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/bacreal/src/main.c

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2020 Legrand North America, LLC.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+/* @file
+ * @brief test BACnet real value encode/decode APIs
+ */
+
+#include <ztest.h>
+#include <bacnet/bacreal.h>
+#include <bacnet/bacdef.h>
+
+/**
+ * @addtogroup bacnet_tests
+ * @{
+ */
+
+/**
+ * @brief Test BACnet real data type (single precision floating point)
+ */
+static void testBACreal(void)
+{
+    float real_value = 3.14159F, test_real_value = 0.0;
+    uint8_t apdu[MAX_APDU] = { 0 };
+    int len = 0, test_len = 0;
+
+    len = encode_bacnet_real(real_value, &apdu[0]);
+    zassert_equal(len, 4, NULL);
+    test_len = decode_real(&apdu[0], &test_real_value);
+    zassert_equal(test_len, len, NULL);
+    zassert_equal(test_real_value, real_value, NULL);
+}
+
+/**
+ * @brief Test BACnet double data type (double precision floating point)
+ */
+static void testBACdouble(void)
+{
+    double double_value = 3.1415927, test_double_value = 0.0;
+    uint8_t apdu[MAX_APDU] = { 0 };
+    int len = 0, test_len = 0;
+
+    len = encode_bacnet_double(double_value, &apdu[0]);
+    zassert_equal(len, 8, NULL);
+    test_len = decode_double(&apdu[0], &test_double_value);
+    zassert_equal(test_len, len, NULL);
+    zassert_equal(test_double_value, double_value, NULL);
+}
+/**
+ * @}
+ */
+
+
+void test_main(void)
+{
+    ztest_test_suite(bacreal_tests,
+     ztest_unit_test(testBACreal),
+     ztest_unit_test(testBACdouble)
+     );
+
+    ztest_run_test_suite(bacreal_tests);
+}