tests: Add a sample for testing natively

This simple unit test runs basic sanity checking on buffers from
net_buf_get. It demonstrates the mocking support in a real-world case,
where it is used to remove the dependency to nano_fifo.

Origin: Original

Signed-off-by: Jaakko Hannikainen <jaakko.hannikainen@intel.com>
Change-Id: If2757823bebbc0fa22b3064a432032cdbccdfe2b
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

tests/unit/net/buf/Makefile

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+include $(ZEPHYR_BASE)/tests/unit/Makefile.unittest

tests/unit/net/buf/main.c

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+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <ztest.h>
+
+#include <net/buf.c>
+
+void nano_fifo_init(struct nano_fifo *fifo) {}
+void nano_fifo_put_list(struct nano_fifo *fifo, void *head, void *tail) {}
+
+nano_context_type_t sys_execution_context_type_get(void)
+{
+	return NANO_CTX_FIBER;
+}
+
+void *nano_fifo_get(struct nano_fifo *fifo, int32_t timeout)
+{
+	return ztest_get_return_value_ptr();
+}
+
+void nano_fifo_put(struct nano_fifo *fifo, void *data)
+{
+	ztest_check_expected_value(data);
+}
+
+#define BUF_COUNT 1
+#define BUF_SIZE 74
+
+static struct nano_fifo bufs_fifo;
+static NET_BUF_POOL(bufs_pool, BUF_COUNT, BUF_SIZE, &bufs_fifo,
+		NULL, sizeof(int));
+
+static void init_pool(void)
+{
+	ztest_expect_value(nano_fifo_put, data, &bufs_pool);
+	net_buf_pool_init(bufs_pool);
+}
+
+static void test_get_single_buffer(void)
+{
+	struct net_buf *buf;
+
+	init_pool();
+
+	ztest_returns_value(nano_fifo_get, bufs_pool);
+	buf = net_buf_get_timeout(&bufs_fifo, 0, TICKS_NONE);
+
+	assert_equal_ptr(buf, &bufs_pool[0], "Returned buffer not from pool");
+	assert_equal(buf->ref, 1, "Invalid refcount");
+	assert_equal(buf->len, 0, "Invalid length");
+	assert_equal(buf->flags, 0, "Invalid flags");
+	assert_equal_ptr(buf->frags, NULL, "Frags not NULL");
+}
+
+void test_main(void)
+{
+	ztest_test_suite(net_buf_test,
+		ztest_unit_test(test_get_single_buffer)
+	);
+
+	ztest_run_test_suite(net_buf_test);
+}

tests/unit/net/buf/testcase.ini

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+[test]
+type = unit
+tags = buf
+timeout = 5