import type { TypeMatcher } from './matcher';
/**
 * Match any string.
 *
 * @param matching An optional string or RegExp to match the string against.
 *   If it's a string, a case-sensitive search will be performed.
 *
 * @example
 * const fn = mock<(x: string, y: string) => number>();
 * when(() => fn(It.isString(), It.isString('bar'))).returns(42);
 *
 * fn('foo', 'baz') // throws
 * fn('foo', 'bar') === 42
 */
export declare const isString: (matching?: string | RegExp) => TypeMatcher<string>;