Package detail

monocart-coverage-reports

cenfun1mMIT2.12.2

A code coverage tool to generate native V8 reports or Istanbul reports.

readme

Monocart Coverage Reports

license build dependencies

🌐 English | 简体中文

JS代码覆盖率工具，用来生成原生的V8或者Istanbul代码覆盖率报告

用法
选项配置
所有支持的报告类型
比较两种报告
如何收集Istanbul覆盖率数据
如何收集V8覆盖率数据
- 用Playwright
- 用Puppeteer
- 从Node.js
- 使用CDPClientAPI
- 参考V8覆盖率的API
过滤V8覆盖率数据
使用 sourcePath 修改源文件路径
为未测试的文件添加空的覆盖率报告
onEnd回调函数
如何忽略未覆盖的代码
多进程支持
如何使用CLI命令行
如何加载配置文件
如何合并覆盖率报告
- 自动合并
- 手动合并
常见问题
- Unexpected coverage
- Unparsable source
- JavaScript heap out of memory
如何调试覆盖率数据和查看sourcemap
如何跟其他框架集成
集成的例子
- Playwright
- c8
- CodeceptJS
- VSCode
- Jest
- Vitest
- Node Test Runner
- Puppeteer
- Cypress
- WebdriverIO
- Storybook Test Runner
- TestCafe
- Selenium Webdriver
- Mocha
- TypeScript
- AVA
- Codecov
- Codacy
- Coveralls
- Sonar Cloud
Contributing
更新日志
感谢

Usage

推荐使用 Node.js 20+.

安装
```
npm install monocart-coverage-reports
```

API

const MCR = require('monocart-coverage-reports');
const mcr = MCR({
  name: 'My Coverage Report - 2024-02-28',
  outputDir: './coverage-reports',
  reports: ["v8", "console-details"],
  cleanCache: true
});
await mcr.add(coverageData);
await mcr.generate();

也可以使用ESM的 import 然后加载配置文件

import { CoverageReport } from 'monocart-coverage-reports';
const mcr = new CoverageReport();
await mcr.loadConfig();

参见多进程支持

CLI

mcr node my-app.js -r v8,console-details

参见命令行

Options

默认选项: lib/default/options.js
选项的类型描述，见 CoverageReportOptions lib/index.d.ts
配置文件

Available Reports

内置V8报告(仅V8格式数据支持):

v8
- 推荐使用:
  - 全新的原生V8覆盖率报告界面，更好的用户体验
  - 支持原生的Bytes覆盖率指标
  - 支持高性能处理大数据
  - 支持任何运行时代码的覆盖率（压缩后的）
  - 支持CSS代码覆盖率（用于分析CSS的冗余代码）
  - 对Sourcemap转换有更好的支持
- 预览: V8 and more

v8-json
- 保存 CoverageResults 到一个json文件 (默认是 coverage-report.json)
- 用于VSCode扩展来显示原生V8代码覆盖率: Monocart Coverage for VSCode

内置Istanbul报告 (V8和Istanbul格式数据都支持):

clover
cobertura
html
- Istanbul html
- V8 to Istanbul
html-spa
json
json-summary
lcov
lcovonly
- V8 lcov.info
- Istanbul lcov.info
none
teamcity
text
text-lcov
text-summary

其他内置报告 (V8和Istanbul格式数据都支持):

codecov 保存覆盖率数据到 Codecov 专属的json文件 (默认是codecov.json), 见例子
codacy 保存覆盖率数据到 Codacy 专属的json文件 (默认是codacy.json)
console-summary 在控制台显示覆盖率概要

console-details 在控制台显示每个文件的覆盖率概要。如果是Github actions，可以使用环境变量FORCE_COLOR: true来强制开启颜色支持

markdown-summary 保存概要信息到markdown文件 (默认是coverage-summary.md)。如果是Github actions, 可以把markdown的内容添加到a job summary
```
cat path-to/coverage-summary.md >> $GITHUB_STEP_SUMMARY
```
markdown-details 保存覆盖率详情到markdown文件 (默认是 coverage-details.md)
- 预览运行结果 runs
raw 只是保存原始覆盖率数据, 用于使用inputDir参数来导入多个原始数据进行合并报告。参见合并覆盖率报告

自定义报告

  {
      reports: [
          [path.resolve('./test/custom-istanbul-reporter.js'), {
              type: 'istanbul',
              file: 'custom-istanbul-coverage.text'
          }],
          [path.resolve('./test/custom-v8-reporter.js'), {
              type: 'v8',
              outputFile: 'custom-v8-coverage.json'
          }],
          [path.resolve('./test/custom-v8-reporter.mjs'), {
              type: 'both'
          }]
      ]
  }

Istanbul自定义报告

例子: ./test/custom-istanbul-reporter.js, see istanbul built-in reporters' implementation for reference.
V8自定义报告

例子: ./test/custom-v8-reporter.js

Multiple Reports:

如何配置多个报告

const MCR = require('monocart-coverage-reports');
const coverageOptions = {
    outputDir: './coverage-reports',
    reports: [
        // build-in reports
        ['console-summary'],
        ['v8'],
        ['html', {
            subdir: 'istanbul'
        }],
        ['json', {
            file: 'my-json-file.json'
        }],
        'lcovonly',

        // custom reports
        // Specify reporter name with the NPM package
        ["custom-reporter-1"],
        ["custom-reporter-2", {
            type: "istanbul",
            key: "value"
        }],
        // Specify reporter name with local path
        ['/absolute/path/to/custom-reporter.js']
    ]
}
const mcr = MCR(coverageOptions);

Compare Reports

如果是V8数据格式使用Istanbul的报告，将自动从V8转换到Istanbul

| | Istanbul | V8 | V8 to Istanbul | | :--------------| :------ | :------ | :---------------------- | | 数据格式 | Istanbul (Object) | V8 (Array) | V8 (Array) | | 输出报告 | Istanbul reports | V8 reports | Istanbul reports | | - Bytes 字节覆盖率 | ❌ | ✅ | ❌ | | - Statements 语句覆盖率 | ✅ | ✅ | ✅ | | - Branches 分支覆盖率 | ✅ | ✅ | ✅ | | - Functions 函数覆盖率 | ✅ | ✅ | ✅ | | - Lines 行覆盖率 | ✅ | ✅ | ✅ | | - Execution counts 函数执行数 | ✅ | ✅ | ✅ | | CSS 覆盖率 | ❌ | ✅ | ✅ | | 压缩过的代码 | ❌ | ✅ | ❌ |

Collecting Istanbul Coverage Data

在收集Istanbul覆盖率数据之前，需要编译源代码来安装Istanbul计数器
- webpack babel-loader: babel-plugin-istanbul, 参见例子: webpack.config-istanbul.js
- 官方CLI: nyc instrument 或API: istanbul-lib-instrument
- vite: vite-plugin-istanbul
- rollup: rollup-plugin-istanbul
- swc: swc-plugin-coverage-instrument
从浏览器
- Istanbul的覆盖率数据会保存到全局的window.__coverage__，直接读取即可, 参见例子: test-istanbul.js
从Node.js
- 同理对于Node.js会保存到全局的global.__coverage__
使用CDP
- getIstanbulCoverage() 参见CDPClient API

Collecting V8 Coverage Data

在收集V8覆盖率数据之前，需要开启构建工具的sourcemap支持，并且不要压缩代码
- webpack: devtool: source-map and mode: development, example webpack.config-v8.js
- rollup: sourcemap: true and treeshake: false
- esbuild: sourcemap: true, treeShaking: false and minify: false
- vite: sourcemap: true and minify: false
浏览器 (仅支持基于Chromium的浏览器)
- 使用Playwright
- 使用Puppeteer
从Node.js
- 从Node.js收集V8覆盖率数据
使用CDP
- 使用CDPClient API收集V8覆盖率数据

Collecting V8 Coverage Data with Playwright

使用Playwright的覆盖接口收集覆盖率数据

await Promise.all([
    page.coverage.startJSCoverage({
        // reportAnonymousScripts: true,
        resetOnNavigation: false
    }),
    page.coverage.startCSSCoverage({
        // Note, anonymous styles (without sourceURLs) are not supported, alternatively, you can use CDPClient
        resetOnNavigation: false
    })
]);

await page.goto("your page url");

const [jsCoverage, cssCoverage] = await Promise.all([
    page.coverage.stopJSCoverage(),
    page.coverage.stopCSSCoverage()
]);

const coverageData = [... jsCoverage, ... cssCoverage];

使用 @playwright/test 的 Automatic fixtures收集覆盖率数据, 见例子: fixtures.ts 参见例子 ./test/test-v8.js, and anonymous, css

Collecting Raw V8 Coverage Data with Puppeteer

使用Puppeteer的覆盖接口收集覆盖率数据，注意Puppeteer默认不会提供原生V8的覆盖率数据，需要设置includeRawScriptCoverage

await Promise.all([
    page.coverage.startJSCoverage({
        // reportAnonymousScripts: true,
        resetOnNavigation: false,
        // provide raw v8 coverage data
        includeRawScriptCoverage: true
    }),
    page.coverage.startCSSCoverage({
        resetOnNavigation: false
    })
]);

await page.goto("your page url");

const [jsCoverage, cssCoverage] = await Promise.all([
    page.coverage.stopJSCoverage(),
    page.coverage.stopCSSCoverage()
]);

// to raw V8 script coverage
const coverageData = [... jsCoverage.map((it) => {
    return {
        source: it.text,
        ... it.rawScriptCoverage
    };
}), ... cssCoverage];

参见: ./test/test-puppeteer.js

Collecting V8 Coverage Data from Node.js

有多种方法可以从Node.js收集V8覆盖率数据:

NODE_V8_COVERAGE=dir
- 使用Node.js环境变量NODE_V8_COVERAGE=dir来启动程序, 然后在进程正常结束之后，覆盖率数据将自动保存到指定的dir目录.
- 从dir目录读取所有的JSON文件，来生成覆盖率报告
- 参见例子:
  
  cross-env NODE_V8_COVERAGE=.temp/v8-coverage-env node ./test/test-node-env.js && node ./test/generate-report.js
V8 API + NODE_V8_COVERAGE
- 如果进程不能正常结束，比如被强制关闭，或者压根就不结束，比如启动了一个服务类的，那么需要手动写入覆盖率数据，这里需要调用接口v8.takeCoverage()
- 参见例子:
  
  cross-env NODE_V8_COVERAGE=.temp/v8-coverage-api node ./test/test-node-api.js
Inspector API
- 首先连接到Node.js的V8 inspector
- 然后使用inspector的覆盖相关API来开启和收集覆盖率数据
- 参见例子:
  
  node ./test/test-node-ins.js
- vm的例子 (注意这里需要使用scriptOffset，因为vm里一般都会加一层包裹代码，需要这个偏移位置来修正覆盖率数据块的位置):
  
  node ./test/test-node-vm.js
CDP API
- 开启Node调试
- 使用CDP的覆盖率接口开启和收集覆盖率数据
- 参见例子:
  
  node --inspect=9229 ./test/test-node-cdp.js
Node Debugging + CDP + NODE_V8_COVERAGE + V8 API
- 如果启动了一个Node服务，可以手动调用v8.takeCoverage()接口来保存覆盖率数据，开启Node调试就可以远程通过CDP连接的Runtime.evaluate，来调用这个接口.
- 参见koa的例子:
  
  node ./test/test-node-koa.js
Child Process + NODE_V8_COVERAGE
- 如果是子进程，可参见命令行

Collecting V8 Coverage Data with `CDPClient` API

CDPClient为MCR提供的内置接口类，用来更便捷的处理覆盖率相关数据，所有的API如下 `js // 开始和停止并收集JS的覆盖率数据 startJSCoverage: () => Promise<void>; stopJSCoverage: () => Promise<V8CoverageEntry[]>;

// 开始和停止并收集CSS的覆盖率数据，支持匿名文件(比如style里的css) startCSSCoverage: () => Promise<void>; stopCSSCoverage: () => Promise<V8CoverageEntry[]>;

// 开始和停止并收集JS和CSS的覆盖率数据 startCoverage: () => Promise<void>; stopCoverage: () => Promise<V8CoverageEntry[]>;

/** 如果开启了NODE_V8_COVERAGE，这个接口用来手动保存当前覆盖率数据 */ writeCoverage: () => Promise<string>;

/** 收集istanbul覆盖率数据 */ getIstanbulCoverage: (coverageKey?: string) => Promise<any>;


- 结合使用Node调试端口`--inspect=9229` 或者浏览器调试端口 `--remote-debugging-port=9229`
```js
const MCR = require('monocart-coverage-reports');
const client = await MCR.CDPClient({
    port: 9229
});
await client.startJSCoverage();
// run your test here
const coverageData = await client.stopJSCoverage();

结合使用 Playwright CDPSession

const { chromium } = require('playwright');
const MCR = require('monocart-coverage-reports');
const browser = await chromium.launch();
const page = await browser.newPage();
const session = await page.context().newCDPSession(page);
const client = await MCR.CDPClient({
  session
});
// both js and css coverage
await client.startCoverage();
// run your test page here
await page.goto("your page url");
const coverageData = await client.stopCoverage();

结合使用 Puppeteer CDPSession

const puppeteer = require('puppeteer');
const MCR = require('monocart-coverage-reports');
const browser = await puppeteer.launch({});
const page = await browser.newPage();
const session = await page.target().createCDPSession();
const client = await MCR.CDPClient({
  session
});
// both js and css coverage
await client.startCoverage();
// run your test page here
await page.goto("your page url");
const coverageData = await client.stopCoverage();

结合使用 Selenium Webdriver WebSocket (仅支持Chrome/Edge浏览器)

const { Builder, Browser } = require('selenium-webdriver');
const MCR = require('monocart-coverage-reports');
const driver = await new Builder().forBrowser(Browser.CHROME).build();
const pageCdpConnection = await driver.createCDPConnection('page');
const session = new MCR.WSSession(pageCdpConnection._wsConnection);
const client = await MCR.CDPClient({
  session
})

V8 Coverage Data API

JavaScript V8代码覆盖官方说明
Playwright的覆盖率接口
Puppeteer的覆盖率接口

DevTools Protocol的覆盖率接口参见 ScriptCoverage 和 v8-coverage

// Coverage data for a source range.
export interface CoverageRange {
  // JavaScript script source offset for the range start.
  startOffset: integer;
  // JavaScript script source offset for the range end.
  endOffset: integer;
  // Collected execution count of the source range.
  count: integer;
}
// Coverage data for a JavaScript function.
/**
* @functionName can be an empty string.
* @ranges is always non-empty. The first range is called the "root range".
* @isBlockCoverage indicates if the function has block coverage information.
  If this is false, it usually means that the functions was never called.
  It seems to be equivalent to ranges.length === 1 && ranges[0].count === 0.
*/
export interface FunctionCoverage {
  // JavaScript function name.
  functionName: string;
  // Source ranges inside the function with coverage data.
  ranges: CoverageRange[];
  // Whether coverage data for this function has block granularity.
  isBlockCoverage: boolean;
}
// Coverage data for a JavaScript script.
export interface ScriptCoverage {
  // JavaScript script id.
  scriptId: Runtime.ScriptId;
  // JavaScript script name or url.
  url: string;
  // Functions contained in the script that has coverage data.
  functions: FunctionCoverage[];
}
export type V8CoverageData = ScriptCoverage[];

JavaScript Runtime	V8 Coverage
Chrome (65%)	✅	Chromium-based
Safari (18%)	❌
Edge (5%)	✅	Chromium-based
Firefox (2%)	❌
Node.js	✅
Deno	❌	issue
Bun	❌

Filtering Results

Using `entryFilter` and `sourceFilter` to filter the results for V8 report

当收集到V8的覆盖数据时，它实际上包含了所有的入口文件的覆盖率数据, 比如有以下3个文件:

dist/main.js
dist/vendor.js
dist/something-else.js

这个时候可以使用entryFilter来过滤这些入口文件. 比如我们不需要看到vendor.js和something-else.js的覆盖率，就可以过滤掉，只剩下1个文件

dist/main.js

如果一个入口文件存在行内或者链接的sourcemap文件，那么我们会尝试读取并解析sourcemap，以获取入口文件包含的所有源文件，并添加到列表。此时如果logging没有设置成debug，那么这个入口文件在成功解出源文件后会被移除

src/index.js
src/components/app.js
node_modules/dependency/dist/dependency.js

这个时候可以使用sourceFilter来过滤这些源文件。比如我们不需要看到源文件dependency.js的覆盖率，就可以过滤掉，最后只剩下如下文件

src/index.js
src/components/app.js

过滤可以使用函数:

const coverageOptions = {
    entryFilter: (entry) => entry.url.indexOf("main.js") !== -1,
    sourceFilter: (sourcePath) => sourcePath.search(/src\//) !== -1
};

也可以使用便捷的minimatch来匹配（推荐）:

const coverageOptions = {
    entryFilter: "**/main.js",
    sourceFilter: "**/src/**"
};

支持多个匹配:

const coverageOptions = {
    entryFilter: {
        '**/node_modules/**': false,
        '**/vendor.js': false,
        '**/src/**': true
    },
    sourceFilter: {
        '**/node_modules/**': false,
        '**/**': true
    }
};

作为CLI参数（JSON字符串，Added in: v2.8）:

mcr --sourceFilter "{'**/node_modules/**':false,'**/**':true}"

注意，这些匹配实际上会转换成一个过滤函数（如下），所以如果一个匹配成功则会直接返回，后面的将不再继续匹配。请注意先后顺序，如果存在包含关系的，可以调整上下顺序，最后如果都未匹配，则默认返回false

const coverageOptions = {
    entryFilter: (entry) => {
        if (minimatch(entry.url, '**/node_modules/**')) { return false; }
        if (minimatch(entry.url, '**/vendor.js')) { return false; }
        if (minimatch(entry.url, '**/src/**')) { return true; }
        return false; // else unmatched
    }
};

Using `filter` instead of `entryFilter` and `sourceFilter`

如果你不想定义两个过滤器，可以使用 filter 选项代替，可以将多个匹配合并在一起. (Added in: v2.8)

const coverageOptions = {
    // combined patterns
    filter: {
        '**/node_modules/**': false,
        '**/vendor.js': false,
        '**/src/**': true
        '**/**': true
    }
};

Resolve `sourcePath` for the Source Files

当一个文件从sourcemap解包，它的路径可能是个虚拟路径, 此时可以使用sourcePath选项来修改文件路径。比如，我们测试了多个dist包的入口文件，它们的源文件可能包含了一些共同的文件，但路径可能不同，如果我们需要相同的文件覆盖率数据可以自动合并，那么需要使用sourcePath来统一这些相同文件的路径

const coverageOptions = {
    sourcePath: (filePath) => {
        // Remove the virtual prefix
        const list = ['my-dist-file1/', 'my-dist-file2/'];
        for (const str of list) {
            if (filePath.startsWith(str)) {
                return filePath.slice(str.length);
            }
        }
        return filePath;
    }
};

它也支持简单key/value的替换:

const coverageOptions = {
    sourcePath: {
        'my-dist-file1/': '', 
        'my-dist-file2/': ''
    }
};

解决文件路径不完整的问题：

const path = require("path")

// MCR coverage options
const coverageOptions = {
    sourcePath: (filePath, info)=> {
        if (!filePath.includes('/') && info.distFile) {
            return `${path.dirname(info.distFile)}/${filePath}`;
        }
        return filePath;
    }
}

Adding Empty Coverage for Untested Files

默认，未测试的文件是不会包含到覆盖率报告的，需要使用all选项来为这些文件添加一个空的覆盖率，也就是0%

const coverageOptions = {
    all: './src',

    // 支持多个目录
    all: ['./src', './lib'],
};

未测试的文件也适用于sourceFilter过滤器. 而且也可以指定自己的filter过滤器 (可以返回文件类型来支持js或css的覆盖率格式):

const coverageOptions = {
    all: {
        dir: ['./src'],
        filter: {
            // exclude files
            '**/ignored-*.js': false,
            '**/*.html': false,
            // empty css coverage
            '**/*.scss': "css",
            '**/*': true
        }
    }
};

我们可能需要编译.ts, .jsx, .vue等等这样的文件, 这样才能被默认的AST解析器解析，以得到更多的覆盖率指标的数据

const path = require("path");
const swc = require("@swc/core");
const coverageOptions = {
    all: {
        dir: ['./src'],
        transformer: async (entry) => {
            const { code, map } = await swc.transform(entry.source, {
                filename: path.basename(entry.url),
                sourceMaps: true,
                isModule: true,
                jsc: {
                    parser: {
                        syntax: "typescript",
                        jsx: true
                    },
                    transform: {}
                }
            });
            entry.source = code;
            entry.sourceMap = JSON.parse(map);
        }
    }
};

onEnd Hook

结束回调可以用来自定义业务需求，比如检测覆盖率是否达标，对比每个指标的thresholds，如果低于要求的值则可以抛出一个错误退出

const EC = require('eight-colors');
const coverageOptions = {
    name: 'My Coverage Report',
    outputDir: './coverage-reports',
    onEnd: (coverageResults) => {
        const thresholds = {
            bytes: 80,
            lines: 60
        };
        console.log('check thresholds ...', thresholds);
        const errors = [];
        const { summary } = coverageResults;
        Object.keys(thresholds).forEach((k) => {
            const pct = summary[k].pct;
            if (pct < thresholds[k]) {
                errors.push(`Coverage threshold for ${k} (${pct} %) not met: ${thresholds[k]} %`);
            }
        });
        if (errors.length) {
            const errMsg = errors.join('\n');
            console.log(EC.red(errMsg));
            // throw new Error(errMsg);
            // process.exit(1);
        }
    }
}

Ignoring Uncovered Codes

使用特定的注释，以v8 ignore开头可以忽略未覆盖的代码:

忽略开始到结束

/* v8 ignore start */
function uncovered() {
}
/* v8 ignore stop */

忽略接下来一行或者多行 `js /* v8 ignore next */ const os = platform === 'wind32' ? 'Windows' : 'Other';

const os = platform === 'wind32' ? 'Windows' /* v8 ignore next */ : 'Other';

// v8 ignore next 3 if (platform === 'linux') { console.log('hello linux'); }

- 兼容支持 [c8 coverage](https://github.com/bcoe/c8/?tab=readme-ov-file#ignoring-all-lines-until-told) 或 [nodejs coverage](https://nodejs.org/docs/latest/api/test.html#collecting-code-coverage) 的语法格式
```js
/* c8 ignore start */
function uncovered() {
}
/* c8 ignore stop */

/* node:coverage disable */
function uncovered() {
}
/* node:coverage enable */

Multiprocessing Support

多进程支持可以很好的解决异步并行的情况。所有的覆盖率数据会保存到[outputDir]/.cache，在报告生成之后，这些缓存数据会被清除。除非开启了调试模式，或者使用了raw报告
主进程，初始化，清理之前的缓存
const MCR = require('monocart-coverage-reports');
const coverageOptions = require('path-to/same-options.js');
const mcr = MCR(coverageOptions);
// clean previous cache before the start of testing
// unless the running environment is new and no cache
mcr.cleanCache();

子进程1, 测试业务1

const MCR = require('monocart-coverage-reports');
const coverageOptions = require('path-to/same-options.js');
const mcr = MCR(coverageOptions);
await mcr.add(coverageData1);

子进程2, 测试业务2

const MCR = require('monocart-coverage-reports');
const coverageOptions = require('path-to/same-options.js');
const mcr = MCR(coverageOptions);
await mcr.add(coverageData2);

主进程，所有测试完成之后

// generate coverage reports after the completion of testing
const MCR = require('monocart-coverage-reports');
const coverageOptions = require('path-to/same-options.js');
const mcr = MCR(coverageOptions);
await mcr.generate();

Command Line

使用mcr命令行将使用NODE_V8_COVERAGE=dir来启动一个子进程运行程序，直到正常退出，然后自动从dir目录来读取覆盖率数据，并生成覆盖率报告

全局安装

npm i monocart-coverage-reports -g
mcr node ./test/specs/node.test.js -r v8,console-details --lcov

本地项目安装

npm i monocart-coverage-reports
npx mcr node ./test/specs/node.test.js -r v8,console-details --lcov

命令行参数直接运行 mcr 或 mcr --help 查看所有CLI的参数
使用 -- 可以隔离子程序参数，以免两种参数混淆
```
mcr -c mcr.config.js -- sub-cli -c sub-cli.config.js
```
参见例子
- Mocha
- TypeScript
- AVA

Config File

根据以下优先级加载配置文件

自定义配置文件（如果没有指定则加载后面的默认配置文件）:
- CLI: mcr --config <my-config-file-path>
- API: await mcr.loadConfig("my-config-file-path")
mcr.config.js
mcr.config.cjs
mcr.config.mjs
mcr.config.json - json format
mcr.config.ts (requires preloading the ts execution module)

Merge Coverage Reports

以下这些使用场景可能需要使用合并覆盖率报告：

多个执行环境，比如Node.js服务端，以及浏览器客户端，比如Next.js
多种测试类型，比如Jest单元测试，以及Playwright的端到端自动化测试
分布式测试，测试结果保存到了多台机器或不同的容器中

Automatic Merging

默认MCR在执行generate()时会自动合并覆盖率数据。所以可以在多进程支持下，多次添加覆盖率数据，最后将自动合并
比如Next.js就可以同时添加前后端覆盖率数据，最后再执行generate()生成覆盖率报告，见例子nextjs-with-playwright
使用Codecov在线覆盖率报告服务，请设置输出codecov报告, 它会生成专属的codecov.json，如果有多个codecov.json文件上传，它们会自动合并数据，参见Codecov 和合并报告说明

Manual Merging

手动合并覆盖率报告需要使用raw报告来导出原始的覆盖率数据到指定的目录

比如，单元测试保存到./coverage-reports/unit/raw，见例子

Jest + jest-monocart-coverage

Vitest + vitest-monocart-coverage

const coverageOptions = {
name: 'My Unit Test Coverage Report',
outputDir: "./coverage-reports/unit",
reports: [
  ['raw', {
      // relative path will be "./coverage-reports/unit/raw"
      // defaults to raw
      outputDir: "raw"
  }],
  ['v8'],
  ['console-details']
]
};

同样的，E2E测试保存到./coverage-reports/e2e/raw. 见例子:
- Playwright + monocart-reporter with coverage API
- Playwright + MCR, see playwright-coverage
- see more Integration Examples

然后创建一个merge-coverage.js文件，使用inputDir参数导入raw数据，来生成合并的覆盖率报告.

// merge-coverage.js
const fs = require('fs');
const { CoverageReport } = require('monocart-coverage-reports');
const inputDir = [
  './coverage-reports/unit/raw',
  './coverage-reports/e2e/raw'
];
const coverageOptions = {
  name: 'My Merged Coverage Report',
  inputDir,
  outputDir: './coverage-reports/merged',

  // filter for both unit and e2e
  entryFilter: {
      '**/node_modules/**': false,
      '**/*': true
  },
  sourceFilter: {
      '**/node_modules/**': false,
      '**/src/**': true
  },

  sourcePath: (filePath, info) => {
      // Unify the file path for the same files
      // For example, the file index.js has different paths:
      // unit: unit-dist/src/index.js
      // e2e: e2e-dist/src/index.js
      // return filePath.replace("unit-dist/", "").replace("e2e-dist/", "")
      return filePath;
  },

  reports: [
      ['v8'],
      ['console-details']
  ],

  onEnd: () => {
      // remove the raw files if it useless
      // inputDir.forEach((p) => {
      //     fs.rmSync(p, {
      //         recursive: true,
      //         force: true
      //     });
      // });
  }
};
await new CoverageReport(coverageOptions).generate();

最后在所有测试完成后运行node path/to/merge-coverage.js. 所有的执行脚本大概如下:

{
  "scripts": {
      "test:unit": "jest",
      "test:e2e": "playwright test",
      "merge-coverage": "node path/to/merge-coverage.js",
      "test": "npm run test:unit && npm run test:e2e && npm run merge-coverage"
  }
}

参见例子： merge-code-coverage

Common issues

常见问题

Unexpected coverage

覆盖率看起来不正确，多数情况是因为sourcemap转换的问题导致的. 可以先尝试设置构建工具的 minify=false 也就是不要压缩代码来解决。下面来看看sourcemap存在问题的具体原因：

const a = tf ? 'true' : 'false';
               ^     ^  ^
              m1     p  m2

上面是经过构建工具编译过的代码，通过AST分析，位置p对应的原始位置是我们要找的，而从sourcemap里仅能找到离p最近的位置映射m1和m2，也就是位置p并没有精确的映射保存到sourcemap里，从而无法直接获取精确的原始位置，但我们能知道p的原始位置应该在m1和m2之间。

参见调试覆盖率和sourcemap

MCR如何解决这个问题:

1, 首先会尝试使用diff-sequences工具来比较m1和m2之间的生成代码和原始代码，找到p对应的字符位置，可以解决绝大多数问题。但是如果代码是非JS格式的，比如Vue模板是HTML，或JSX这些，不管怎么比较也是很难精确找到对应位置的，甚至此时的sourcemap本身都比较乱。
2, 然后就是通过分析AST，找到所有的functions, statements 和 branches，因为V8覆盖率本身不提供这些指标的覆盖率. (对于分支覆盖暂不支持AssignmentPattern类型，因为即使分析AST也无法从V8覆盖率找到它的数据)。

Unparsable source

源码无法解析问题。由上面我们知道MCR通过分析源码的AST获取更多指标的覆盖率信息，但源码如果不是标准的 ECMAScript，比如ts, jsx这些，那么分析的时候就会报错，此时我们可以手动来编译这些文件（可行但不推荐）.

import * as fs from "fs";
import * as path from "path";
import { fileURLToPath } from "url";
import * as TsNode from 'ts-node';
const coverageOptions = {
    onEntry: async (entry) => {
        const filePath = fileURLToPath(entry.url)
        const originalSource = fs.readFileSync(filePath).toString("utf-8");
        const fileName = path.basename(filePath);
        const tn = TsNode.create({});
        const source = tn.compile(originalSource, fileName);
        entry.fake = false;
        entry.source = source;
    }
}

JavaScript heap out of memory

内存溢出问题可能出现在有太多的原生V8覆盖率文件要处理. 我们可以使用Node.js的一个选项来增加内存使用:

- run: npm run test:coverage
    env:
        NODE_OPTIONS: --max-old-space-size=8192

Debug for Coverage and Sourcemap

当你觉得覆盖率存在问题的时候，MCR支持自行调试来核验覆盖率的准确性
首先打开调试设置logging: 'debug'
const coverageOptions = {
  logging: 'debug',
  reports: [
      ['v8'],
      ['console-details']
  ]
};
调试模式下，也就是logging为debug的时候, 原始的覆盖率数据将保留在[outputDir]/.cache缓存目录下，不会删除，如果使用了raw报告，那么位置变为[outputDir]/raw下，这样我们可以打开v8报告的html文件，通过下面新增的一些调试帮助信息来核对覆盖率

调试sourcemap可以直接使用Source Map Visualization （esbuild作者提供的sourcemap在线查看器）

生成额外的source和sourcemap文件到cache或raw文件夹

const coverageOptions = {
  logging: 'debug',
  sourceMap: true
};

使用环境变量MCR_LOG_TIME显示时间日志
```
process.env.MCR_LOG_TIME = true
```

Integration with Any Testing Framework

通用集成方案

通过API接口在程序集成
- 首先，要自行收集覆盖率数据，然后，添加到报告实例 await mcr.add(coverageData)
- 最后，生成覆盖率报告 await mcr.generate()
- 参见多进程支持
通过CLI命令行与其他命令行集成
- 直接在其他命令行前面添加mcr的命令行即可 mcr your-cli --your-arguments
- 参见命令行

Integration Examples

Playwright

playwright-coverage - Example for Playwright coverage reports
playwright-bdd-coverage - Example for Playwright BDD coverage reports
monocart-reporter - Playwright custom reporter, supports generating Code coverage report
Coverage for component testing with monocart-reporter:
Coverage for Next.js, both server side and client side:
- nextjs-with-playwright
- nextjs-with-playwright-istanbul
Coverage for Remix:
- remix-with-playwright
see Collecting V8 Coverage Data with Playwright

c8

c8 has integrated MCR as an experimental feature since v10.1.0

c8 --experimental-monocart --reporter=v8 --reporter=console-details node foo.js

CodeceptJS

CodeceptJS is a BDD + AI testing framework for e2e testing, it has integrated MCR since v3.5.15, see plugins/coverage

VSCode

Monocart Coverage for VSCode - Shows native V8 code coverage in VSCode

Jest

jest-monocart-coverage - Jest custom reporter for coverage reports
merge-code-coverage - Example for merging code coverage (Jest unit + Playwright e2e sharding)

Vitest

vitest-monocart-coverage - Vitest custom provider module for coverage reports
merge-code-coverage-vitest - Example for merging code coverage (Vitest unit + Playwright e2e sharding)

Node Test Runner

node-monocart-coverage - Custom reporter for Node test runner for coverage

Puppeteer

jest-puppeteer-coverage - Example for Jest puppeteer coverage
maplibre-gl-js - Example for Jest (unit) + Puppeteer (e2e) + Codecov
see Collecting Raw V8 Coverage Data with Puppeteer

Cypress

cypress-monocart-coverage - Cypress plugin for coverage reports

WebdriverIO

wdio-monocart-service - WebdriverIO service for coverage reports

Storybook Test Runner

storybook-monocart-coverage - Example for Storybook V8 coverage reports

TestCafe

testcafe-reporter-coverage - TestCafe custom reporter for coverage reports

Selenium Webdriver

selenium-webdriver-coverage - Example for Selenium Webdriver V8 coverage reports

Mocha

mcr mocha ./test/**/*.js

TypeScript

tsx

cross-env NODE_OPTIONS="--import tsx" npx mcr tsx ./src/example.ts
cross-env NODE_OPTIONS="--import tsx" npx mcr mocha ./test/**/*.ts
# Node.js v18.19.0 +
mcr --import tsx tsx ./src/example.ts
mcr --import tsx mocha ./test/**/*.ts

ts-node

cross-env NODE_OPTIONS="--loader ts-node/esm --no-warnings" npx mcr ts-node ./src/example.ts
cross-env NODE_OPTIONS="--loader ts-node/esm --no-warnings" npx mcr mocha ./test/**/*.ts

AVA

mcr ava

Codecov

Supports native codecov built-in report (specification)

const coverageOptions = {
  outputDir: "./coverage-reports",
  reports: [
      ['codecov']
  ]
};

Github actions: `yml

name: Codecov uses: codecov/codecov-action@v4 with:

  token: ${{ secrets.CODECOV_TOKEN }}
  files: ./coverage-reports/codecov.json

Codacy

Using lcov report:

const coverageOptions = {
  outputDir: "./coverage-reports",
  lcov: true
};

Github actions: `yml

name: Codacy Coverage Reporter uses: codacy/codacy-coverage-reporter-action@v1 with:

  project-token: ${{ secrets.CODACY_PROJECT_TOKEN }}
  coverage-reports: ./docs/mcr/lcov.info

Coveralls