/**
 * Diff Reporter — Compare two test run JSON reports side-by-side.
 *
 * Shows: new passes, new failures, regressions, improvements.
 */
import type { SuiteResult } from '../types';
export interface RunDiff {
    newPasses: string[];
    newFailures: string[];
    regressions: string[];
    improvements: string[];
    unchanged: string[];
    summary: {
        oldTotal: number;
        newTotal: number;
        oldPassed: number;
        newPassed: number;
        oldFailed: number;
        newFailed: number;
    };
}
/**
 * Compare two suite results to find regressions and improvements.
 */
export declare function diffRuns(oldRun: SuiteResult, newRun: SuiteResult): RunDiff;
/**
 * Format a run diff for terminal display.
 */
export declare function formatRunDiff(diff: RunDiff): string;
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