feat: add test helpers for database setup and file content comparison

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

src/tests/common/test_helpers.rs

@@ -89,3 +89,34 @@ pub fn test_compression_engine(engine: &dyn crate::compression_engine::Compressi
     
     assert_eq!(test_data, decompressed.as_slice());
 }
+
+/// Create a test database with some initial data
+pub fn create_test_db_with_data() -> (TempDir, Connection, PathBuf) {
+    let (temp_dir, conn, db_path) = create_temp_db();
+    
+    // Add some test items
+    let item1 = crate::db::Item {
+        id: None,
+        ts: chrono::Utc::now(),
+        size: Some(100),
+        compression: crate::compression_engine::CompressionType::None.to_string(),
+    };
+    db::insert_item(&conn, item1).expect("Failed to insert item1");
+    
+    let item2 = crate::db::Item {
+        id: None,
+        ts: chrono::Utc::now(),
+        size: Some(200),
+        compression: crate::compression_engine::CompressionType::LZ4.to_string(),
+    };
+    db::insert_item(&conn, item2).expect("Failed to insert item2");
+    
+    (temp_dir, conn, db_path)
+}
+
+/// Assert that two paths point to files with identical content
+pub fn assert_files_equal(path1: &PathBuf, path2: &PathBuf) {
+    let content1 = std::fs::read(path1).expect("Failed to read first file");
+    let content2 = std::fs::read(path2).expect("Failed to read second file");
+    assert_eq!(content1, content2, "Files {:?} and {:?} have different content", path1, path2);
+}