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Test if your HTML matches GOV.UK Frontend

You can use our test fixtures to check you’re outputting the same HTML that GOV.UK Frontend uses, when you:

Using the HTML test files

If you installed GOV.UK Frontend with Node.js package manager (npm), you can find the fixtures.json file for each component in the node_modules/govuk-frontend/govuk/components/COMPONENT-NAME/ folder, where COMPONENT-NAME is the name of the component.

For example, you can find the fixtures.json file for the button component in the node_modules/govuk-frontend/govuk/components/button/ folder:

  "component": "button",
  "fixtures": [
      "name": "default",
      "options": {
        "text": "Save and continue"
      "html": "<button class=\"govuk-button\" data-module=\"govuk-button\">\n  Save and continue\n</button>",
      "hidden": false
      "name": "secondary button",
      "options": {
        "text": "Find address",
        "classes": "govuk-button--secondary"
      "html": "<button class=\"govuk-button govuk-button--secondary\" data-module=\"govuk-button\">\nFind address\n</button>",
      "hidden": false

Each object in the fixtures list is a different example of the component, where:

  • name is the name of the example
  • options are the options that generate this example’s html
  • html is the HTML that GOV.UK Frontend outputs with these options
  • hidden is true if the fixture does not look or behave differently to the other fixtures provided

Do not include hidden fixtures when you use fixtures for manual or visual regression testing.

For each example, pass options into your own macro and check the generated HTML matches html.

If your HTML does not match exactly, you’ll need to write your tests so they ignore known differences. For example your framework may add extra whitespace or attributes to your HTML.