Add test for broken symlinks

Cargo.toml

@@ -49,6 +49,11 @@ name = "fs_symlink_dir"
 path = "tests/fs_symlink_dir.rs"
 harness = false
 
+[[test]]
+name = "fs_broken_symlink"
+path = "tests/fs_broken_symlink.rs"
+harness = false
+
 [[test]]
 name = "fs_null"
 path = "tests/fs_null.rs"

tests/fs_broken_symlink.rs

@@ -0,0 +1,30 @@
+use std::fs;
+use std::os::unix::fs as unixfs;
+use std::path::PathBuf;
+
+use birdcage::error::Error;
+use birdcage::{Birdcage, Exception, Sandbox};
+use tempfile::NamedTempFile;
+
+fn main() {
+    // Setup a symlink without target.
+    let tempfile = NamedTempFile::new().unwrap();
+    let tempfile_path = tempfile.path().to_path_buf();
+    let symlink_str = tempfile_path.to_string_lossy() + "_tmpfile";
+    let symlink = PathBuf::from(symlink_str.as_ref());
+    unixfs::symlink(&tempfile, &symlink).unwrap();
+    drop(tempfile);
+    assert!(!tempfile_path.exists());
+
+    // Sandbox exception fails with invalid path error.
+    let mut birdcage = Birdcage::new();
+    let result = birdcage.add_exception(Exception::Read(symlink.clone()));
+    assert!(matches!(result, Err(Error::InvalidPath(_))));
+    birdcage.lock().unwrap();
+
+    // Read/Write results in error.
+    let result = fs::read_to_string(&symlink);
+    assert!(result.is_err());
+    let result = fs::write(&symlink, "bob");
+    assert!(result.is_err());
+}