Add basic tests

library/std/src/os/unix/fs.rs

@@ -17,6 +17,10 @@
 #[allow(unused_imports)]
 use io::{Read, Write};
 
+// Tests for this module
+#[cfg(test)]
+mod tests;
+
 /// Unix-specific extensions to [`fs::File`].
 #[stable(feature = "file_offset", since = "1.15.0")]
 pub trait FileExt {

library/std/src/os/unix/fs/tests.rs

@@ -0,0 +1,57 @@
+use super::*;
+
+#[test]
+fn read_vectored_at() {
+    let msg = b"preadv is working!";
+    let dir = crate::sys_common::io::test::tmpdir();
+
+    let filename = dir.join("preadv.txt");
+    {
+        let mut file = fs::File::create(&filename).unwrap();
+        file.write_all(msg).unwrap();
+    }
+    {
+        let file = fs::File::open(&filename).unwrap();
+        let mut buf0 = [0; 4];
+        let mut buf1 = [0; 3];
+
+        let mut iovec = [io::IoSliceMut::new(&mut buf0), io::IoSliceMut::new(&mut buf1)];
+
+        let n = file.read_vectored_at(&mut iovec, 4).unwrap();
+
+        assert!(n == 4 || n == 7);
+        assert_eq!(&buf0, b"dv i");
+
+        if n == 7 {
+            assert_eq!(&buf1, b"s w");
+        }
+    }
+}
+
+#[test]
+fn write_vectored_at() {
+    let msg = b"pwritev is not working!";
+    let dir = crate::sys_common::io::test::tmpdir();
+
+    let filename = dir.join("preadv.txt");
+    {
+        let mut file = fs::File::create(&filename).unwrap();
+        file.write_all(msg).unwrap();
+    }
+    let expected = {
+        let file = fs::File::options().write(true).open(&filename).unwrap();
+        let buf0 = b"    ";
+        let buf1 = b"great  ";
+
+        let iovec = [io::IoSlice::new(buf0), io::IoSlice::new(buf1)];
+
+        let n = file.write_vectored_at(&iovec, 11).unwrap();
+
+        assert!(n == 4 || n == 11);
+
+        if n == 4 { b"pwritev is     working!" } else { b"pwritev is     great  !" }
+    };
+
+    let content = fs::read(&filename).unwrap();
+    assert_eq!(&content, expected);
+}