feat: add helper functions for creating temporary files with random binary content and asserting file sizes

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/tests/common/test_helpers.rs

@@ -183,3 +183,24 @@ pub fn create_nested_temp_dir_structure(dir: &TempDir) -> (PathBuf, PathBuf, Pat
     
     (level1, level2, level3)
 }
+
+/// Create a temporary file with random binary content of specified size
+pub fn create_temp_file_with_random_binary_content(dir: &TempDir, filename: &str, size: usize) -> PathBuf {
+    use rand::Rng;
+    let mut rng = rand::thread_rng();
+    let random_data: Vec<u8> = (0..size).map(|_| rng.gen()).collect();
+    create_temp_file_with_binary_content(dir, filename, &random_data)
+}
+
+/// Assert that a file has the expected size
+pub fn assert_file_size(file_path: &PathBuf, expected_size: u64) {
+    let actual_size = get_file_size(file_path);
+    assert_eq!(actual_size, expected_size, "File {:?} has size {} but expected {}", file_path, actual_size, expected_size);
+}
+
+/// Create multiple temporary files with content in a directory
+pub fn create_multiple_temp_files_with_content(dir: &TempDir, files: &[(&str, &str)]) -> Vec<PathBuf> {
+    files.iter().map(|(filename, content)| {
+        create_temp_file_with_content(dir, filename, content)
+    }).collect()
+}