Added lseek test

tests/fs-test.rs

@@ -3,7 +3,7 @@ mod common;
 use std::{fs::read_to_string, path::PathBuf};
 
 use byte_unit::{Byte, Unit};
-use common::{build_hermit_bin, check_result, remove_file_if_exists};
+use common::{build_hermit_bin, check_result, remove_file_if_exists, run_simple_vm};
 use uhyvelib::{
 	params::{Output, Params},
 	vm::UhyveVm,
@@ -67,3 +67,11 @@ fn uhyvefilemap_test() {
 	check_result(&res);
 	verify_file_equals(&output_path, "Hello, world!");
 }
+
+#[test]
+fn lseek_test() {
+	env_logger::try_init().ok();
+	let bin_path = build_hermit_bin("lseek");
+	let res = run_simple_vm(bin_path);
+	check_result(&res);
+}

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

@@ -0,0 +1,30 @@
+use std::{
+	fs::OpenOptions,
+	io::{prelude::*, SeekFrom},
+};
+
+#[cfg(target_os = "hermit")]
+use hermit as _;
+
+fn main() {
+	let mut buf: [u8; 10] = [0; 10];
+	println!("Initial Buffer: {buf:?}");
+	let mut f = OpenOptions::new()
+		.read(true)
+		.write(true)
+		.create(true)
+		.open("/root/foo.txt")
+		.unwrap();
+	f.write(&[
+		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
+	])
+	.unwrap();
+	f.read(&mut buf).unwrap();
+	assert_eq!(buf, [0; 10]);
+	println!("file pre-seek: {buf:?}");
+
+	f.seek(SeekFrom::Start(5)).unwrap();
+	f.read(&mut buf).unwrap();
+	println!("file post-seek: {buf:?}");
+	assert_eq!(buf, [5, 6, 7, 8, 9, 10, 11, 12, 13, 14]);
+}