/**
 * Reads and writes files.
 */
export declare type IFileSystem = Readonly<{
    /**
     * Reads a file.
     *
     * @param filePath   Path to the file.
     * @returns Promise for the contents of the file.
     */
    readFile(filePath: string): Promise<string>;
    /**
     * Writes a file.
     *
     * @param filePath   Path to the file.
     * @param contents   New contents for the file.
     * @returns Promise for writing to the file.
     */
    writeFile(filePath: string, contents: string): Promise<void>;
}>;
/**
 * Reads and writes files.
 */
export declare class FileSystem implements IFileSystem {
    /**
     * Reads a file.
     *
     * @param filePath   Path to the file.
     * @returns Promise for the contents of the file.
     */
    readFile(filePath: string): Promise<string>;
    /**
     * Writes a file.
     *
     * @param filePath   Path to the file.
     * @param contents   New contents for the file.
     * @returns Promise for writing to the file.
     */
    writeFile(filePath: string, contents: string): Promise<void>;
}