[test] Improve fdcan test on STM32

test/modm/platform/fdcan/fdcan_test.cpp

@@ -79,10 +79,14 @@ FdcanTest::testBuffers()
 			modm::can::ExtendedIdentifier(0),
 			modm::can::ExtendedMask(0));
 
+	// send (RxBufferSize + 2) messages, exceeds internal peripheral queue size (3
+	// msgs) as well as the software queue size, but not both added together. So
+	// no message should get lost.
+	const uint_fast16_t numberOfMsgs = Fdcan1::RxBufferSize + 2;
+
 	modm::can::Message message{0x4711, 0};
-	// send 8 messages, exceeds internal peripheral queue size
-	for (uint_fast8_t i = 0; i <= 8; ++i) {
-		message.setLength(i);
+	for (uint_fast16_t i = 0; i <= numberOfMsgs; ++i) {
+		message.setLength(i % 8);
 		for (uint_fast8_t dataIndex = 0; dataIndex < i; ++dataIndex) {
 			message.data[dataIndex] = i;
 		}
@@ -93,11 +97,11 @@ FdcanTest::testBuffers()
 
 	// try to receive same messages
 	modm::can::Message receivedMessage;
-	for (uint_fast8_t i = 0; i <= 8; ++i) {
+	for (uint_fast16_t i = 0; i <= numberOfMsgs; ++i) {
 		TEST_ASSERT_TRUE(Fdcan1::getMessage(receivedMessage));
 
 		TEST_ASSERT_EQUALS(receivedMessage.getIdentifier(), 0x4711u);
-		TEST_ASSERT_EQUALS(receivedMessage.getLength(), i);
+		TEST_ASSERT_EQUALS(receivedMessage.getLength(), (i % 8));
 
 		for (uint_fast8_t dataIndex = 0; dataIndex < i; ++dataIndex) {
 			TEST_ASSERT_EQUALS(receivedMessage.data[dataIndex], i);