test: first example of tests on host

examples/aes_ecb.rs

@@ -24,7 +24,8 @@ fn main() -> ! {
     let mut rcc = dp.RCC.freeze(Config::hsi16());
     let mut delay = cp.SYST.delay(rcc.clocks);
 
-    compile_error!("The chip does not have an AES unit >:{");
+    // WARN: Make sure your chip has AES
+    panic!("The chip does not have an AES unit >:");
     let aes = hal::aes::AES::new(dp.AES, &mut rcc);
     let mut ecb_stream = aes.enable(<dyn hal::aes::Mode>::ecb_encrypt(), AES_KEY);
     let mut encbuf: [[u8; 16]; 4] = [[0; 16]; 4];

examples/test-on-host.rs

@@ -0,0 +1,51 @@
+#![cfg_attr(not(test), no_main)]
+#![no_std]
+
+#[cfg(not(test))]
+extern crate panic_halt;
+
+#[cfg(not(test))]
+use cortex_m_rt::entry;
+use hal::{pac, prelude::*, rcc::Config};
+
+#[cfg(not(test))]
+#[entry]
+fn main() -> ! {
+    let dp = pac::Peripherals::take().unwrap();
+    let cp = cortex_m::Peripherals::take().unwrap();
+
+    // Configure the clock.
+    let mut rcc = dp.RCC.freeze(Config::hsi16());
+
+    // Acquire the GPIOA peripheral. This also enables the clock for GPIOA in
+    // the RCC register.
+    let gpioa = dp.GPIOA.split(&mut rcc);
+
+    // Configure PA5 as output.
+    let mut led = gpioa.pa5.into_push_pull_output();
+
+    // Get the delay provider.
+    let mut delay = cp.SYST.delay(rcc.clocks);
+
+    loop {
+        led.set_high().unwrap();
+        delay.delay_ms(500_u16);
+
+        led.set_low().unwrap();
+        delay.delay_ms(500_u16);
+    }
+}
+
+#[cfg(test)]
+fn main() -> ! {
+    loop {}
+}
+
+#[cfg(test)]
+mod tests {
+
+    #[test]
+    fn test_it_works() {
+        assert!(true)
+    }
+}