example of test and calling C from rust

rust/src/lib.rs

@@ -1,15 +1,28 @@
 #![no_std]
 
-use core::panic::PanicInfo;
-
 /// This function is called on panic.
+#[cfg(not(test))]
 #[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
+fn panic(_info: &core::panic::PanicInfo) -> ! {
     loop {}
 }
 
-
 #[no_mangle]
 pub extern "C" fn get_rust_u8() -> u8 {
-    9
+    //9
-}   
+    unsafe { get_c_u8() }
+}
+
+extern "C" {
+    fn get_c_u8() -> u8;
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+
+    #[test]
+    fn it_works() {
+        assert_eq!(get_rust_u8(), 9);
+    }
+}

src/main.c

@@ -58,6 +58,10 @@
 
 #define MAX_LIST 20
 
+uint8_t get_c_u8(void) {
+    return 20;
+}
+
 struct glyph
 {
     int xoff;