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Unit test writer

Generate a test suite for your code: happy paths, edge cases, error paths.

Run this template ≈ 1,000 Runs

Sample: input → output

Input

Code: function add(a, b) { return a + b; }

Sample outputMade on 27 October 2026

import { describe, expect, it } from 'vitest';

const add = (a: number, b: number): number => a + b;

describe('add', () => { describe('happy paths', () => { it('adds two positive numbers', () => { // Arrange const a = 2; const b = 3;

  // Act
  const result = add(a, b);

  // Assert
  expect(result).toBe(5);
});

it('adds two negative numbers', () => {
  // Arrange
  const a = -2;
  const b = -3;

  // Act
  const result = add(a, b);

  // Assert
  expect(result).toBe(-5);
});…

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add(a, b) Adds two values using JavaScript’s + operator. Parameters Name Type Constraints a any None. If either operand is a string, string concatenation may occur. b any None. If either operand is a string, string concatenation may occur. Returns any — The result of evaluating a + b. Errors This function does not explicitly throw errors. JavaScript may throw a TypeError for incompatible operand types, such as mixing a bigint with a number. Example const result = add(2, 3);…

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The Cost of Doing Nothing Assumptions Replace these inputs with internal figures as needed: 20 engineers run or wait for CI an average of 2 times per day 220 working days per year Fully loaded engineering cost: $150/hour Current suite duration: 45 minutes Estimated productive time lost per run: 15 minutes due to parallel work, context switching, and delayed feedback 5 flaky-test reruns or investigations per day, averaging 20 minutes each 2 production incidents last quarter traced to untested paths Average incident cost:…

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