feat(backlight): add tests

app/tests/backlight/behavior_keymap.dtsi

@@ -0,0 +1,34 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include <dt-bindings/zmk/backlight.h>
+
+/ {
+	chosen {
+		zmk,backlight = &backlight;
+	};
+
+	backlight: leds {
+		compatible = "gpio-leds";
+		led_0 {
+			gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+			label = "Backlight LED 0";
+		};
+		led_1 {
+			gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
+			label = "Backlight LED 1";
+		};
+	};
+
+	keymap {
+		compatible = "zmk,keymap";
+		label ="Default keymap";
+
+		default_layer {
+			bindings = <
+				&bl BL_INC &bl BL_DEC
+				&bl BL_ON  &bl BL_OFF
+			>;
+		};
+	};
+};