# Test Implementation: Async File I/O Operations

## Issue #603: Refactor synchronous file I/O operations to be asynchronous

### Overview

This document outlines the testing strategy and implementation for the
asynchronous file I/O operations refactored in Issue #603. The tests verify that
the async versions of the functions maintain the same behavior as their
synchronous counterparts while providing non-blocking I/O operations.

### Test Files

The following test files have been created:

1. `tests/libs/file/test_async_file_ops.py`
2. `tests/libs/file/test_async_save.py`
3. `tests/libs/file/test_async_concat_files.py`
4. `tests/libs/file/test_async_concat.py`
5. `tests/libs/file/test_async_process.py`

### Test Strategy

For each refactored function, we have implemented tests that:

1. Verify basic functionality
2. Test error handling
3. Compare performance between sync and async versions
4. Test edge cases

All tests use the `pytest.mark.asyncio` decorator to run in an async context.

### Test Implementation Details

#### 1. `test_async_file_ops.py`

Tests for the async versions of functions in `file_ops.py`:

- `test_async_read_file`: Tests reading a file asynchronously and handling file
  not found errors.
- `test_async_copy_file`: Tests copying a file asynchronously and handling file
  not found errors.
- `test_async_get_file_size`: Tests getting a file's size asynchronously and
  handling file not found errors.
- `test_async_list_files`: Tests listing files in a directory asynchronously,
  with filtering by extension and handling directory not found errors.
- `test_sync_vs_async_read_performance`: Compares the performance of synchronous
  and asynchronous file reading.

#### 2. `test_async_save.py`

Tests for the async versions of functions in `save.py`:

- `test_async_save_to_file`: Tests saving text to a file asynchronously.
- `test_async_save_chunks`: Tests saving chunks to files asynchronously.
- `test_sync_vs_async_save_performance`: Compares the performance of synchronous
  and asynchronous file saving.

#### 3. `test_async_concat_files.py`

Tests for the async version of `concat_files` in `concat_files.py`:

- `test_async_concat_files`: Tests concatenating files asynchronously.
- `test_async_concat_files_with_directory`: Tests concatenating files from a
  directory asynchronously.
- `test_async_concat_files_with_threshold`: Tests concatenating files with a
  threshold asynchronously.
- `test_async_concat_files_return_files`: Tests concatenating files with
  return_files=True asynchronously.
- `test_sync_vs_async_concat_files_performance`: Compares the performance of
  synchronous and asynchronous file concatenation.

#### 4. `test_async_concat.py`

Tests for the async version of `concat` in `concat.py`:

- `test_async_concat`: Tests concatenating text asynchronously.
- `test_async_concat_with_directory`: Tests concatenating files from a directory
  asynchronously.
- `test_async_concat_with_threshold`: Tests concatenating with a threshold
  asynchronously.
- `test_async_concat_with_exclude_patterns`: Tests concatenating with exclude
  patterns asynchronously.
- `test_async_concat_return_files`: Tests concatenating with return_files=True
  asynchronously.
- `test_sync_vs_async_concat_performance`: Compares the performance of
  synchronous and asynchronous concatenation.

#### 5. `test_async_process.py`

Tests for the async versions of functions in `process.py`:

- `test_async_dir_to_files`: Tests processing a directory to files
  asynchronously.
- `test_async_file_to_chunks`: Tests processing a file to chunks asynchronously.
- `test_async_chunk_with_text`: Tests chunking text asynchronously.
- `test_async_chunk_with_file`: Tests chunking a file asynchronously.
- `test_async_chunk_with_directory`: Tests chunking a directory asynchronously.
- `test_async_chunk_with_custom_reader`: Tests chunking with a custom reader
  asynchronously.
- `test_sync_vs_async_process_performance`: Compares the performance of
  synchronous and asynchronous processing.

### Performance Testing

For performance testing, we:

1. Create multiple files with reasonably large content
2. Measure the time taken by both synchronous and asynchronous versions
3. Print the results for comparison

Note: The performance tests acknowledge that async operations might not always
be faster for small files or simple operations due to the overhead of async
machinery. The real benefit of async I/O is seen with many concurrent operations
or when I/O operations are slow (like network requests).

### Edge Cases and Error Handling

The tests cover the following edge cases and error handling:

1. File not found errors
2. Directory not found errors
3. Permission errors (with ignore_errors=True)
4. Empty files
5. Files with different encodings
6. Directories with nested structures
7. Files with different extensions

### Test Results

All tests pass successfully, verifying that the async versions of the functions
maintain the same behavior as their synchronous counterparts while providing
non-blocking I/O operations.

### Future Improvements

1. Add more comprehensive performance tests with larger files and more
   concurrent operations
2. Test with actual network file systems to better demonstrate the benefits of
   async I/O
3. Add tests for the output file functionality in `async_chunk`
