test a bit more

tests/run-pass/fs.rs

@@ -80,6 +80,7 @@ fn test_seek() {
     let mut file = File::open(&path).unwrap();
     let mut contents = Vec::new();
     file.read_to_end(&mut contents).unwrap();
+    assert_eq!(bytes, contents.as_slice());
     // Test that seeking to the beginning and reading until EOF gets the text again.
     file.seek(SeekFrom::Start(0)).unwrap();
     let mut contents = Vec::new();