Add test for statx

Author: pvdrz

tests/run-pass/fs.rs

@@ -1,7 +1,7 @@
 // ignore-windows: File handling is not implemented yet
 // compile-flags: -Zmiri-disable-isolation
 
-use std::fs::{File, remove_file};
+use std::fs::{File, remove_file, metadata};
 use std::io::{Read, Write, ErrorKind};
 
 fn main() {
@@ -21,7 +21,15 @@ fn main() {
     // Reading until EOF should get the whole text.
     file.read_to_end(&mut contents).unwrap();
     assert_eq!(bytes, contents.as_slice());
-    // Removing file should succeed
+
+    // Test that the file metadata is correct.
+    let metadata = metadata(&path).unwrap();
+    // `path` should point to a file.
+    assert!(metadata.is_file());
+    // The size of the file must be equal to the number of written bytes.
+    assert_eq!(bytes.len() as u64, metadata.len());
+
+    // Removing file should succeed.
     remove_file(&path).unwrap();
 
     // The two following tests also check that the `__errno_location()` shim is working properly.