diff --git a/tests/drivers/uart/uart_async_api/src/test_uart_async.c b/tests/drivers/uart/uart_async_api/src/test_uart_async.c
index 0506ff0a01f..3f56bbe1d80 100644
--- a/tests/drivers/uart/uart_async_api/src/test_uart_async.c
+++ b/tests/drivers/uart/uart_async_api/src/test_uart_async.c
@@ -24,12 +24,12 @@ K_SEM_DEFINE(rx_buf_coherency, 0, 255);
 K_SEM_DEFINE(rx_buf_released, 0, 1);
 K_SEM_DEFINE(rx_disabled, 0, 1);
 
-ZTEST_BMEM volatile bool failed_in_isr;
+static ZTEST_BMEM volatile bool failed_in_isr;
 static ZTEST_BMEM const struct device *const uart_dev =
 	DEVICE_DT_GET(UART_NODE);
 
 static void read_abort_timeout(struct k_timer *timer);
-K_TIMER_DEFINE(read_abort_timer, read_abort_timeout, NULL);
+static K_TIMER_DEFINE(read_abort_timer, read_abort_timeout, NULL);
 
 
 static void init_test(void)
@@ -100,7 +100,7 @@ struct test_data {
 #if NOCACHE_MEM
 static struct test_data tdata __used __NOCACHE;
 #else
-ZTEST_BMEM struct test_data tdata;
+static ZTEST_BMEM struct test_data tdata;
 #endif /* NOCACHE_MEM */
 
 static void test_single_read_callback(const struct device *dev,
@@ -331,14 +331,14 @@ static __aligned(32) uint8_t chained_read_buf_0[8] __used __NOCACHE;
 static __aligned(32) uint8_t chained_read_buf_1[8] __used __NOCACHE;
 static __aligned(32) uint8_t chained_cpy_buf[10] __used __NOCACHE;
 #else
-ZTEST_BMEM uint8_t chained_read_buf_0[8];
-ZTEST_BMEM uint8_t chained_read_buf_1[8];
-ZTEST_BMEM uint8_t chained_cpy_buf[10];
+static ZTEST_BMEM uint8_t chained_read_buf_0[8];
+static ZTEST_BMEM uint8_t chained_read_buf_1[8];
+static ZTEST_BMEM uint8_t chained_cpy_buf[10];
 #endif /* NOCACHE_MEM */
-ZTEST_BMEM volatile uint8_t rx_data_idx;
-ZTEST_BMEM uint8_t rx_buf_idx;
+static ZTEST_BMEM volatile uint8_t rx_data_idx;
+static ZTEST_BMEM uint8_t rx_buf_idx;
 
-ZTEST_BMEM uint8_t *read_ptr;
+static ZTEST_BMEM uint8_t *read_ptr;
 
 static uint8_t *chained_read_buf[2] = {chained_read_buf_0, chained_read_buf_1};
 
@@ -422,9 +422,9 @@ ZTEST_USER(uart_async_chain_read, test_chained_read)
 #if NOCACHE_MEM
 static __aligned(32) uint8_t double_buffer[2][12] __used __NOCACHE;
 #else
-ZTEST_BMEM uint8_t double_buffer[2][12];
+static ZTEST_BMEM uint8_t double_buffer[2][12];
 #endif /* NOCACHE_MEM */
-ZTEST_DMEM uint8_t *next_buf = double_buffer[1];
+static ZTEST_DMEM uint8_t *next_buf = double_buffer[1];
 
 static void test_double_buffer_callback(const struct device *dev,
 				 struct uart_event *evt, void *user_data)
@@ -497,10 +497,10 @@ ZTEST_USER(uart_async_double_buf, test_double_buffer)
 static __aligned(32) uint8_t test_read_abort_rx_buf[2][100] __used __NOCACHE;
 static __aligned(32) uint8_t test_read_abort_read_buf[100] __used __NOCACHE;
 #else
-ZTEST_BMEM uint8_t test_read_abort_rx_buf[2][100];
-ZTEST_BMEM uint8_t test_read_abort_read_buf[100];
+static ZTEST_BMEM uint8_t test_read_abort_rx_buf[2][100];
+static ZTEST_BMEM uint8_t test_read_abort_read_buf[100];
 #endif /* NOCACHE_MEM */
-ZTEST_BMEM int test_read_abort_rx_cnt;
+static ZTEST_BMEM int test_read_abort_rx_cnt;
 
 static void test_read_abort_callback(const struct device *dev,
 			      struct uart_event *evt, void *user_data)
@@ -613,12 +613,12 @@ ZTEST_USER(uart_async_read_abort, test_read_abort)
 
 }
 
-ZTEST_BMEM volatile size_t sent;
-ZTEST_BMEM volatile size_t received;
+static ZTEST_BMEM volatile size_t sent;
+static ZTEST_BMEM volatile size_t received;
 #if NOCACHE_MEM
 static __aligned(32) uint8_t test_rx_buf[2][100] __used __NOCACHE;
 #else
-ZTEST_BMEM uint8_t test_rx_buf[2][100];
+static ZTEST_BMEM uint8_t test_rx_buf[2][100];
 #endif /* NOCACHE_MEM */
 
 static void test_write_abort_callback(const struct device *dev,
@@ -776,12 +776,12 @@ ZTEST_USER(uart_async_timeout, test_forever_timeout)
 
 
 #if NOCACHE_MEM
-const uint8_t chained_write_tx_bufs[2][10] = {"Message 1", "Message 2"};
+static const uint8_t chained_write_tx_bufs[2][10] = {"Message 1", "Message 2"};
 #else
-ZTEST_DMEM uint8_t chained_write_tx_bufs[2][10] = {"Message 1", "Message 2"};
+static ZTEST_DMEM uint8_t chained_write_tx_bufs[2][10] = {"Message 1", "Message 2"};
 #endif /* NOCACHE_MEM */
-ZTEST_DMEM bool chained_write_next_buf = true;
-ZTEST_BMEM volatile uint8_t tx_sent;
+static ZTEST_DMEM bool chained_write_next_buf = true;
+static ZTEST_BMEM volatile uint8_t tx_sent;
 
 static void test_chained_write_callback(const struct device *dev,
 				 struct uart_event *evt, void *user_data)
@@ -863,12 +863,12 @@ static __aligned(32) uint8_t long_rx_buf[RX_LONG_BUFFER] __used __NOCACHE;
 static __aligned(32) uint8_t long_rx_buf2[RX_LONG_BUFFER] __used __NOCACHE;
 static __aligned(32) uint8_t long_tx_buf[TX_LONG_BUFFER] __used __NOCACHE;
 #else
-ZTEST_BMEM uint8_t long_rx_buf[RX_LONG_BUFFER];
-ZTEST_BMEM uint8_t long_rx_buf2[RX_LONG_BUFFER];
-ZTEST_BMEM uint8_t long_tx_buf[TX_LONG_BUFFER];
+static ZTEST_BMEM uint8_t long_rx_buf[RX_LONG_BUFFER];
+static ZTEST_BMEM uint8_t long_rx_buf2[RX_LONG_BUFFER];
+static ZTEST_BMEM uint8_t long_tx_buf[TX_LONG_BUFFER];
 #endif /* NOCACHE_MEM */
-ZTEST_BMEM volatile uint8_t evt_num;
-ZTEST_BMEM size_t long_received[2];
+static ZTEST_BMEM volatile uint8_t evt_num;
+static ZTEST_BMEM size_t long_received[2];
 
 static void test_long_buffers_callback(const struct device *dev,
 				struct uart_event *evt, void *user_data)