How to perform accessibility testing in Angular and Storybook

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Accessibility testing is an important aspect of Angular and Storybook development because applications should be accessible to disabled individuals. For example, people who suffer from color blindness can not see red and green, and developers should render texts in different colors. When developing accessible applications in Angular, we can add aria attributes to HTML templates and apply colors with high contrast to satisfy accessibility compliances.

While working on this Angular project, accessibility is not a top priority of mine because my main focus is functionality. Moreover, I am not expert of this area and would require tool to help me identify accessibility violations.

Fortunately, Storybook provides a11y add-on that runs story books against WCAG standard to identify violations to help developers build accessible components in Angular.

In this post, we learn the installation Storybook a11y add-on, verify the results of accessibility testing, fix violations and eventually pass the WCAG rules in both Angular and Storybook.

let's go

Caveats of Storybook add-ons

Storybook application and its add-ons need to have the same version. In my example, the version of a11y add-on that I used is 6.3.12.

Install Storybook a11y add-on

First, we install the new dependency with the exact version, 6.3.12.

npm install --save-exact @storybook/addon-a11y@6.3.12

Then, append "@storybook/addon-a11y" to addons array within ./storybook/main.js.

module.exports = {
  "addons": [
     ... existing addons ...

Launch Storybook application

// package.json 

"scripts": {    
    "docs:json": "compodoc -p ./tsconfig.json -e json -d .",
    "storybook": "npm run docs:json && start-storybook -p 6006",

Second, we type npm run storybook on the terminal to launch the Storybook application.

we can fix all accessibility violations

Verify the results of accessibility testing in Storybook

If a11y is set up properly, we will see a new Accessibility tab on the panel. When clicking the tab, we can see three new sub-tabs: Violations, Passed and Incomplete. Our objective is to achieve 0 violation and test result is either passed or incomplete.

A couple of stories share the following violation:

“Ensures the contrast between foreground and background colors meets WCAG 2 AA contrast ratio thresholds”.

When we check the “Highlight results” checkbox, we see a dashed rectangle on the Submit button. If we change the background color of the button, the accessibility rule should pass.

Similarly, the add-on reports a violation in the story of Food Menu Options. The rule, “Ensures select element has an accessible name”, describes the select input is missing at least arial-label attribute.

To validate my assumption, expand the accordion to read supplementary explanation. The content panel contains “More info…” link that links to WGAC rule page.

Click the link to navigate to the rule page that describes various examples to fix the problem.

Next, we fix the accessibility issues such that none of the storybooks has violations.

Fix accessibility violations in Storybook

Make background color of button to dark indigo

Due to the violations, we apply dark background color in .btn-indigo class in the global stylesheet.

// style.scss

.btn-indigo {
  @apply rounded-md p-2 bg-indigo-600 hover:bg-indigo-400 text-white;

The old value is bg-indigo-500 and the new value is bg-indigo-600

Add aria-label to select food input

Next, we add arial-label attributes to the elements of the template to fix the other violation.

// food-menu-options.component.ts

<section class="flex justify-end p-3 pr-0" aria-label="select food section">
  <form [formGroup]="form" aria-label="select food form">
      <select class="pl-2 w-[200px] text-base" name="option" formControlName="option" aria-label="select food">
         <option value="all" aria-label="show all">Show all</option>
         <option value="available" aria-label="show available">Show available only</option>
         <option value="soldOut" aria-label="show sold out">Show sold out</option>

Re-test accessibility in Storybook

Neither story has violation and the application practices good web accessibility.

Final thought

Storybook facilitates development of web accessibility by offering a11y add-on to illustrate violations. Error messages are clear and provide visual aid to highlight elements that cause the violations. Then, developers can analyze the information and tackle the violations iteratively until the components comply to the WCAG standard.

This is the end of the blog post and I hope you like the content and continue to follow my learning experience in Angular and Storybook.


  1. Repo:
  2. Tailwind:
  3. Storybook Addon PostCSS: