tests: drivers: can: api: add virtual CAN TX <-> RX Jumper

Remove the need for the can_transceiver fixture by assigning the CAN TX
and CAN RX lines to the same GPIO pin to allow for testing without a
transceiver or physical jumper.

Signed-off-by: Eric Holmberg <eric.holmberg@northriversystems.co.nz>

tests/drivers/can/api/testcase.yaml

@@ -10,9 +10,5 @@ tests:
       - drivers
       - can
     extra_args: DTC_OVERLAY_FILE=twai-enable.overlay
-    harness: console
-    harness_config:
-      # actual CAN transceiver or shorted CAN RX/TX pins required for board testing
-      fixture: can_transceiver
     filter: dt_compat_enabled("espressif,esp32-twai")
     platform_allow: esp32c3_devkitm

tests/drivers/can/api/twai-enable.overlay

@@ -4,6 +4,27 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+/* Enable CAN bus */
 &twai {
-        status = "okay";
+	status = "okay";
+	pinctrl-0 = <&twai_default>;
+	pinctrl-names = "default";
+	bus-speed = <125000>;
+
+	can-transceiver {
+		max-bitrate = <1000000>;
+	};
+};
+
+&pinctrl {
+	twai_default: twai_default {
+		group1 {
+			pinmux = <TWAI_RX_GPIO5>;
+			output-enable;	/* enable internal loopback */
+		};
+		group2 {
+			pinmux = <TWAI_TX_GPIO5>;
+			input-enable;	/* enable internal loopback */
+		};
+};
 };