Add a panic handler test

Cargo.toml

@@ -4,6 +4,10 @@ version = "0.1.0"
 authors = ["Philipp Oppermann <dev@phil-opp.com>"]
 edition = "2018"
 
+[[test]]
+name = "panic_handler"
+harness = false
+
 [dependencies]
 bootloader = "0.6.0"
 volatile = "0.2.3"

tests/panic_handler.rs

@@ -0,0 +1,69 @@
+#![no_std]
+#![no_main]
+#![feature(panic_info_message)]
+
+use core::{fmt::{self, Write}, panic::PanicInfo};
+use blog_os::{serial_print, serial_println, QemuExitCode, exit_qemu};
+
+const MESSAGE: &str = "Example panic message from panic_handler test";
+const PANIC_LINE: u32 = 14; // adjust this when moving the `panic!` call
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    serial_print!("panic_handler... ");
+    panic!(MESSAGE); // must be in line `PANIC_LINE` 
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {   
+    check_location(info);
+    check_message(info);
+
+    serial_println!("[ok]");
+    exit_qemu(QemuExitCode::Success);
+    loop {}
+}
+
+fn fail(error: &str) -> ! {
+    serial_println!("[failed]");
+    serial_println!("{}", error);
+    exit_qemu(QemuExitCode::Failed);
+    loop {}
+}
+
+fn check_location(info: &PanicInfo) {
+    let location = info.location().unwrap_or_else(|| fail("no location"));
+    if location.file() != file!() {
+        fail("file name wrong");
+    }
+    if location.line() != PANIC_LINE {
+        fail("file line wrong");
+    }
+}
+
+fn check_message(info: &PanicInfo) {
+    let message = info.message().unwrap_or_else(|| fail("no message"));
+    let mut compare_message = CompareMessage { equals: false };
+    write!(&mut compare_message, "{}", message).unwrap_or_else(|_| fail("write failed"));
+    if !compare_message.equals {
+        fail("message not equal to expected message");
+    }
+}
+
+/// Compares a `fmt::Arguments` instance with the `MESSAGE` string
+/// 
+/// To use this type, write the `fmt::Arguments` instance to it using the
+/// `write` macro. If a message component matches `MESSAGE`, the equals
+/// field is set to true.
+struct CompareMessage {
+    equals: bool,
+}
+
+impl fmt::Write for CompareMessage {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        if s == MESSAGE {
+            self.equals = true;
+        }
+        Ok(())
+    }
+}