/** When tests fail, we often want to print things out.
 * Most of the time it's just a simple string,
 * but sometimes it's something computationally intensive.
 * TestLabel gives us the best of both worlds
 */
export type TestLabel = string | (() => string);
export declare const TestLabel: {
    or: (a: TestLabel | null | undefined, b: TestLabel) => TestLabel;
    asString: (l: TestLabel) => string;
    asStringOr: (a: TestLabel | null | undefined, b: TestLabel) => string;
    map: (l: TestLabel, f: (s: string) => TestLabel) => TestLabel;
    concat: (a: TestLabel, b: TestLabel) => TestLabel;
};