diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index e91387a81f..1399a14929 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -796,6 +796,7 @@
 	gpio-wdt {
 		gpios = <&gpio_a 7 0>;
 		compatible = "linux,wdt-gpio";
+		hw_margin_ms = <100>;
 		always-running;
 	};
 
@@ -1278,6 +1279,7 @@
 
 	wdt0: wdt@0 {
 		compatible = "sandbox,wdt";
+		hw_margin_ms = <200>;
 	};
 
 	axi: axi@0 {
diff --git a/test/dm/wdt.c b/test/dm/wdt.c
index abff853a02..ee615f0e14 100644
--- a/test/dm/wdt.c
+++ b/test/dm/wdt.c
@@ -12,6 +12,8 @@
 #include <dm/test.h>
 #include <test/test.h>
 #include <test/ut.h>
+#include <linux/delay.h>
+#include <watchdog.h>
 
 /* Test that watchdog driver functions are called */
 static int dm_test_wdt_base(struct unit_test_state *uts)
@@ -73,3 +75,55 @@ static int dm_test_wdt_gpio(struct unit_test_state *uts)
 	return 0;
 }
 DM_TEST(dm_test_wdt_gpio, UT_TESTF_SCAN_FDT);
+
+static int dm_test_wdt_watchdog_reset(struct unit_test_state *uts)
+{
+	struct sandbox_state *state = state_get_current();
+	struct udevice *gpio_wdt, *sandbox_wdt;
+	struct udevice *gpio;
+	const u64 timeout = 42;
+	const int offset = 7;
+	uint reset_count;
+	int val;
+
+	ut_assertok(uclass_get_device_by_driver(UCLASS_WDT,
+						DM_DRIVER_GET(wdt_gpio), &gpio_wdt));
+	ut_assertnonnull(gpio_wdt);
+	ut_assertok(uclass_get_device_by_driver(UCLASS_WDT,
+						DM_DRIVER_GET(wdt_sandbox), &sandbox_wdt));
+	ut_assertnonnull(sandbox_wdt);
+	ut_assertok(uclass_get_device_by_name(UCLASS_GPIO, "base-gpios", &gpio));
+	ut_assertnonnull(gpio);
+
+	/* Neither device should be "started", so watchdog_reset() should be a no-op. */
+	reset_count = state->wdt.reset_count;
+	val = sandbox_gpio_get_value(gpio, offset);
+	watchdog_reset();
+	ut_asserteq(reset_count, state->wdt.reset_count);
+	ut_asserteq(val, sandbox_gpio_get_value(gpio, offset));
+
+	/* Start both devices. */
+	ut_assertok(wdt_start(gpio_wdt, timeout, 0));
+	ut_assertok(wdt_start(sandbox_wdt, timeout, 0));
+
+	/* Make sure both devices have just been pinged. */
+	timer_test_add_offset(100);
+	watchdog_reset();
+	reset_count = state->wdt.reset_count;
+	val = sandbox_gpio_get_value(gpio, offset);
+
+	/* The gpio watchdog should be pinged, the sandbox one not. */
+	timer_test_add_offset(30);
+	watchdog_reset();
+	ut_asserteq(reset_count, state->wdt.reset_count);
+	ut_asserteq(!val, sandbox_gpio_get_value(gpio, offset));
+
+	/* After another ~30ms, both devices should get pinged. */
+	timer_test_add_offset(30);
+	watchdog_reset();
+	ut_asserteq(reset_count + 1, state->wdt.reset_count);
+	ut_asserteq(val, sandbox_gpio_get_value(gpio, offset));
+
+	return 0;
+}
+DM_TEST(dm_test_wdt_watchdog_reset, UT_TESTF_SCAN_FDT);