export declare const MATCHER_SYMBOL: unique symbol;
export type MatcherDiffer = (actual: any) => {
    actual: any;
    expected: any;
};
export type MatcherOptions = {
    /**
     * Will be called when printing the diff between an expectation and the
     * (mismatching) received arguments.
     *
     * With this function you can pretty print the `actual` and `expected` values
     * according to your matcher's logic.
     *
     * @param actual The actual value received by this matcher, same as the one
     *   in `matches`.
     *
     * @example
     * const neverMatcher = It.matches(() => false, {
     *   getDiff: (actual) => ({ actual, expected: 'never' })
     * });
     *
     * when(() => fn(neverMatcher)).thenReturn(42);
     *
     * fn(42);
     * // - Expected
     * // + Received
     * //
     * //   - 'never'
     * //   + 42
     */
    getDiff: MatcherDiffer;
    /**
     * Will be called when printing arguments for an unexpected or unmet expectation.
     *
     * @example
     * const neverMatcher = It.matches(() => false, {
     *   toString: () => 'never'
     * });
     * when(() => fn(neverMatcher)).thenReturn(42);
     *
     * fn(42);
     * // Unmet expectations:
     * // when(() => fn(never)).thenReturn(42)
     */
    toString: () => string;
};
/**
 * You MUST use {@link It.matches} to create this branded type.
 */
export interface Matcher extends MatcherOptions {
    [MATCHER_SYMBOL]: boolean;
    /**
     * Will be called with the received value and should return whether it matches
     * the expectation.
     */
    matches: (actual: any) => boolean;
}
/**
 * This takes the shape of T to satisfy call sites, but strong-mock will only
 * care about the matcher type.
 */
export type TypeMatcher<T> = T & Matcher;
/**
 * Used to test if an expectation is an argument is a custom matcher.
 */
export declare function isMatcher(f: unknown): f is Matcher;
export declare const getMatcherDiffs: (matchers: Matcher[], args: unknown[]) => {
    actual: unknown[];
    expected: unknown[];
};
/**
 * Create a custom matcher.
 *
 * @param predicate Will receive the actual value and return whether it matches the expectation.
 * @param options
 * @param options.toString An optional function that should return a string that will be
 *   used when the matcher needs to be printed in an error message. By default,
 *   it stringifies `predicate`.
 * @param options.getDiff An optional function that will be called when printing the
 *   diff for a failed expectation. It will only be called if there's a mismatch
 *   between the expected and received values i.e. `predicate(actual)` fails.
 *   By default, the `toString` method will be used to format the expected value,
 *   while the received value will be returned as-is.
 *
 * @example
 * // Create a matcher for positive numbers.
 * const fn = mock<(x: number) => number>();
 * when(() => fn(It.matches(x => x >= 0))).thenReturn(42);
 *
 * fn(2) === 42
 * fn(-1) // throws
 */
export declare const matches: <T>(predicate: (actual: T) => boolean, options?: Partial<MatcherOptions>) => TypeMatcher<T>;