Jest 單元測試 — Coverage

參考文章：讓 Jest 為你的 Code 做測試-基礎用法教學

🔖 文章索引

1. Setting coverage directory path
2. Setting npm script
3. Example

Setting coverage directory path

// jest.config.js

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  coverageDirectory: 'wwwroot/__test__/coverage'
};

Setting npm script

// package.json

{
  ...
  "scripts": {
    "test" : "jest --env=jsdom --coverage"
  }
  ...
}

Example

依照下方 sum.test.ts 執行 npm run test

// wwwroot/ts/utilities/sum.ts

export default function (a: number, b:number) {
    if (b) {
        return a + b;
    } else {
        return a;
    }
}

// wwwroot/__test__/sum.test.ts

import sum from "../ts/utilities/sum";

test("adds 1 + 2 to equal 3", () => {
    // Arrange
    const x: number = 1;
    const y: number = 2;
    const expectedIf: number = 3;
    // const expectedElse: number = 1;
    
    // Act
    let actIf: number = sum(x, y);
    // @ts-ignore
    // let actElse: number = sum(x);
    
    // Assert
    expect(actIf).toBe(expectedIf);
    // expect(actElse).toBe(expectedElse);
});

所產出的報告 ( 如下圖 ) 會用紅色標示出沒有寫到測試的地方