chore: Add test for overwriting files

src/tests.rs

@@ -1,6 +1,7 @@
 use super::*;
 use std::fs::create_dir_all;
 use std::fs::File;
+use std::io::read_to_string;
 #[cfg(unix)]
 use std::os::unix::fs::{symlink, PermissionsExt};
 
@@ -75,6 +76,39 @@ fn copy_subdir() {
     std::fs::remove_dir_all("source").unwrap();
 }
 
+#[test]
+fn copy_overwrite() {
+    use std::fs::File;
+    use std::io::Write;
+
+    let source_dir = "overwrite_source";
+    let dest_dir = "overwrite_dest";
+
+    std::env::set_var("RUST_LOG", "debug");
+    let _ = env_logger::try_init();
+    create_dir_all(source_dir).unwrap();
+    create_dir_all(dest_dir).unwrap();
+    File::create(format!("{source_dir}/a.txt")).unwrap();
+    let mut file_b = File::create(format!("{source_dir}/b.txt")).unwrap();
+
+    let contents = "Contents changed";
+    // Copy once, both files are empty
+    CopyBuilder::new(source_dir, dest_dir).run().unwrap();
+    // write something to file b so we can check if we overwrite it
+    write!(file_b, "{contents}").unwrap();
+    // perform a second copy
+    CopyBuilder::new(source_dir, dest_dir)
+        .overwrite(true)
+        .run()
+        .unwrap();
+    // make sure the contents of b are now changed
+    let s = read_to_string(File::open(format!("{dest_dir}/b.txt")).unwrap()).unwrap();
+    assert!(s == contents, "Destination was not overwritten");
+
+    std::fs::remove_dir_all(source_dir).unwrap();
+    std::fs::remove_dir_all(dest_dir).unwrap();
+}
+
 #[test]
 fn copy_exclude() {
     std::env::set_var("RUST_LOG", "DEBUG");