Coverage

Coverage gathers information about parts of JavaScript and CSS that were used by the page.

An example of using JavaScript coverage to produce Istanbul report for page load:

note

Coverage APIs are only supported on Chromium-based browsers.

const { chromium } = require('playwright');
const v8toIstanbul = require('v8-to-istanbul');

(async () => {
  const browser = await chromium.launch();
  const page = await browser.newPage();
  await page.coverage.startJSCoverage();
  await page.goto('https://chromium.org');
  const coverage = await page.coverage.stopJSCoverage();
  for (const entry of coverage) {
    const converter = v8toIstanbul('', 0, { source: entry.source });
    await converter.load();
    converter.applyCoverage(entry.functions);
    console.log(JSON.stringify(converter.toIstanbul()));
  }
  await browser.close();
})();

Methods​

startCSSCoverage​

Returns coverage is started

Usage

await coverage.startCSSCoverage();
await coverage.startCSSCoverage(options);

Arguments

• options Object (optional)

  • resetOnNavigation boolean (optional)

    Whether to reset coverage on every navigation. Defaults to true.

Returns

• Promise<void>

startJSCoverage​

Returns coverage is started

note

Anonymous scripts are ones that don't have an associated url. These are scripts that are dynamically created on the page using eval or new Function. If reportAnonymousScripts is set to true, anonymous scripts will have __playwright_evaluation_script__ as their URL.

Usage

await coverage.startJSCoverage();
await coverage.startJSCoverage(options);

Arguments

• options Object (optional)

  • reportAnonymousScripts boolean (optional)

    Whether anonymous scripts generated by the page should be reported. Defaults to false.

  • resetOnNavigation boolean (optional)

    Discouraged

    Settings this to false may still reset on navigations.

    Whether to reset coverage on every navigation. Defaults to true. Note that passing false does not guarantee that coverage persists through navigations, due to browser architecture limitations.

Returns

• Promise<void>

stopCSSCoverage​

Returns the array of coverage reports for all stylesheets

note

CSS Coverage doesn't include dynamically injected style tags without sourceURLs.

Usage

await coverage.stopCSSCoverage();

Returns

• Promise<Array<Object>>

  • url string

    StyleSheet URL

  • text string (optional)

    StyleSheet content, if available.

  • ranges Array<Object>

    • start number

      A start offset in text, inclusive

    • end number

      An end offset in text, exclusive

    StyleSheet ranges that were used. Ranges are sorted and non-overlapping.

stopJSCoverage​

Returns the array of coverage reports for all scripts

note

JavaScript Coverage doesn't include anonymous scripts by default. However, scripts with sourceURLs are reported.

Usage

await coverage.stopJSCoverage();

Returns

• Promise<Array<Object>>

  • url string

    Script URL

  • scriptId string

    Script ID

  • source string (optional)

    Script content, if applicable.

  • functions Array<Object>

    • functionName string

    • isBlockCoverage boolean

    • ranges Array<Object>

      • count number

      • startOffset number

      • endOffset number

    V8-specific coverage format.