test: improve output information

- Print to stdout as soon as the kernel successfully boots
- Print to stdout in run_simple_vm to make it clear that the kernel has
  been compiled
- Clarify the test-kernel being built, as the "name mismatch" between
  fs-test.rs and create_file.rs can be a bit confusing
- Add newline between build_hermit_bin + run_simple_vm output and
  output coming from the kernel
- Minor linguistic improvements

These changes may seem redundant to the trained eye (for example,
it is safe to assume that the output starting with "frequency: ..."
is from the kernel, thus everything that follows is from the kernel),
but can be very helpful to beginners.

Based on local changes that I created for personal use, so as to better
understand the debugging process.

tests/common.rs

@@ -11,8 +11,9 @@ use uhyvelib::{params::Params, vm::UhyveVm};
 /// Returns a path to the build binary.
 pub fn build_hermit_bin(kernel: impl AsRef<Path>) -> PathBuf {
 	let kernel = kernel.as_ref();
-	println!("Building Kernel {}", kernel.display());
 	let kernel_src_path = Path::new("tests/test-kernels");
+	println!("Building test kernel: {}", kernel.display());
+
 	let cmd = Command::new("cargo")
 		.arg("build")
 		.arg("-Zbuild-std=std,panic_abort")
@@ -26,7 +27,8 @@ pub fn build_hermit_bin(kernel: impl AsRef<Path>) -> PathBuf {
 		.current_dir(kernel_src_path)
 		.status()
 		.expect("failed to execute `cargo build`");
-	assert!(cmd.success(), "Test binaries could not be build");
+
+	assert!(cmd.success(), "Test binaries could not be built.");
 	[
 		kernel_src_path,
 		Path::new("target/x86_64-unknown-hermit/debug"),
@@ -39,6 +41,7 @@ pub fn build_hermit_bin(kernel: impl AsRef<Path>) -> PathBuf {
 /// Small wrapper around [`Uhyve::run`] with default parameters for a small and
 /// simple Uhyve vm
 pub fn run_simple_vm(kernel_path: PathBuf) {
+	println!("Launching kernel {}", kernel_path.display());
 	let params = Params {
 		verbose: true,
 		cpu_count: 2.try_into().unwrap(),

tests/gdb.rs

@@ -47,6 +47,7 @@ symbol-file {bin_path} -o 0x400000
 break gdb::main
 continue
 
+next
 next
 next
 pipe print _x|cat >> {output_path}

tests/test-kernels/src/bin/create_file.rs

@@ -4,6 +4,8 @@ use std::{fs::File, io::prelude::*};
 use hermit as _;
 
 fn main() {
+	println!("Hello from create_file!");
+
 	let mut file = File::create("/root/foo.txt").unwrap();
 	file.write_all(b"Hello, world!").unwrap();
 }

tests/test-kernels/src/bin/gdb.rs

@@ -4,6 +4,8 @@ use hermit as _;
 static mut WATCH: u8 = 2;
 
 fn main() {
+	println!("Hello from gdb!");
+
 	let _x = 5;
 	opaque(_x);
 	let _x = 3.5;

tests/test-kernels/src/bin/serial.rs

@@ -27,7 +27,7 @@ pub fn virtual_to_physical(virtual_address: VirtAddr) -> Option<GuestPhysAddr> {
 }
 
 fn main() {
-	println!("Test");
+	println!("Hello from serial!");
 
 	let mut serial_byte_port = Port::new(HypercallAddress::Uart as u16);
 	for c in "ABCD\n".bytes() {