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WCAG 2 Test Rules

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About WCAG 2 Test Rules

Proposed Error message describes invalid form field value

Description

This rule checks that text error messages provided when the user completes a form field with invalid values or using an invalid format, identify the cause of the error or how to fix the error.

Applicability

This rule applies to each HTML element that has one of the following semantic roles:

Note: The list of applicable semantic roles is derived by taking all the ARIA 1.1 roles that:

Expectation 1

Each test target either has no form field error indicators, or at least one of the form field error indicators allows the identification of the related test target, through text, or through non-text content, or through presentation.

Note: This rule does not test form field error indicators shown on a different page than that of the test target.

Note: A single form field error indicator can be related to multiple test targets. For example, an error message at the top of a form can list all the form fields that are required and are empty.

Note: A single test target can be related to multiple form field error indicators. For example, a text field can have a red border around it, an error icon adjacent to it, an error message below it, and another error message at the top of the form. All of these are error indicators for the same form field.

Expectation 2

Each test target either has no form field error indicators, or at least one of the form field error indicators describes:

in text that is visible.

Expectation 3

Each test target either has no form field error indicators, or at least one of the form field error indicators describes:

in text that is included in the accessibility tree or included in the accessible name or accessible description of the test target.

Assumptions

There are currently no assumptions.

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

Bibliography

Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This input element has a form field error indicator that identifies it (by referencing its label), describes the cause of the error and how to resolve it.

<form>
	<label for="age">Age (years)</label>
	<input type="number" id="age" aria-describedby="error" value="0" />
	<span id="error">Invalid value for age. Age must be at least 1.</span><br />
	<input type="button" value="Submit" />
</form>

Passed Example 2

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This multiple input elements share a form field error indicator that identifies the elements unfilled (by referencing their labels), describes the cause of the error and how to resolve it.

<form>
	<p id="error"><strong>
		Name and color cannot be empty. Please complete all required fields.
	</strong></p>
	<fieldset>
		<legend>Shipping</legend>
		<label for="name">Name (required)</label>
		<input type="text" id="name" required />
		<br />
		<label for="address">Address</label>
		<input type="text" id="address" />
	</fieldset>
	<fieldset>
		<legend>Pick a color (required)</legend>
		<label><input type="radio" name="color" value="blue" required />Blue</label>
		<label><input type="radio" name="color" value="yellow" />Yellow</label>
	</fieldset>
	<input type="button" value="Submit" aria-describedby="error" />
</form>

Passed Example 3

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This input element does not have a form field error indicator.

<form>
	<label for="filter">Product filter</label>
	<input type="text" id="filter" />
	<input type="button" value="filter" />
	<p>To see all products, leave the field empty.</p>
</form>

Failed

Failed Example 1

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These multiple input elements share a form field error indicator but its message does not identify the elements that caused the error nor describes the cause of the error.

<form>
	<div id="error">Please fill the field correctly.</div>
	<label for="age">Age (years)</label>
	<input type="number" id="age" />
	<label for="name">Name</label>
	<input type="text" id="name" />
	<input type="button" value="Submit" />
</form>

Failed Example 2

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This input element has a form field error indicator but its message does not describe the cause of the error.

<form>
	<label for="age">Age (years)</label>
	<input type="number" id="age" />
	<span id="error">Please enter the correct text.</span><br />
	<input type="button" value="Submit" />
</form>

Failed Example 3

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This input element has a form field error indicator that identifies it (by referencing its label) and describes the cause of the error but the message is not visible.

<form>
	<label for="age">Age (years)</label>
	<input type="number" id="age" value="0" />
	<span id="error" style="display: none;">Invalid value for age. Age must be at least 1.</span><br />
	<input type="button" value="Submit" aria-describedby="error" />
</form>

Failed Example 4

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This input element has a form field error indicator that identifies it (by referencing its label) and describes the cause of the error but the message is not included in the accessibility tree.

<form>
	<label for="age">Age (years)</label>
	<input type="number" id="age" value="0" />
	<span id="error" aria-hidden="true">Invalid value for age. Age must be at least 1.</span><br />
	<input type="button" value="Submit" />
</form>

Failed Example 5

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These multiple input elements share a form field error indicator. The message describes the cause of the error but does not allow to identify the elements that caused the error because the same label is used in different fieldsets.

<form>
	<fieldset>
		<legend>Shipping</legend>
		<label for="shippingName">Name</label>
		<input type="text" id="shippingName" required />
		<label for="shippingAddress">Address</label>
		<input type="text" id="shippingAddress" required />
	</fieldset>
	<fieldset>
		<legend>Billing</legend>
		<label for="billingName">Name</label>
		<input type="text" id="billingName" />
		<label for="billingAddress">Address</label>
		<input type="text" id="billingAddress" />
	</fieldset>
	<span id="error">All required fields must be filled.<br />Please fill Name.<br />Please fill Address</span><br />
	<input type="button" value="Submit" />
</form>

Inapplicable

Inapplicable Example 1

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There are no elements with any of the required semantic roles.

<p>This is a paragraph.</p>

Glossary

Accessible Name

The accessible name is the programmatically determined name of a user interface element that is included in the accessibility tree.

The accessible name is calculated using the accessible name and description computation.

For native markup languages, such as HTML and SVG, additional information on how to calculate the accessible name can be found in HTML Accessibility API Mappings 1.0, Accessible Name and Description Computation (working draft) and SVG Accessibility API Mappings, Name and Description (working draft).

For more details, see examples of accessible name.

Note: As per the accessible name and description computation, each element always has an accessible name. When no accessible name is provided, the element will nonetheless be assigned an empty ("") one.

Note: As per the accessible name and description computation, accessible names are flat string trimmed of leading and trailing whitespace. Notably, it is not possible for a non-empty accessible name to be composed only of whitespace since these must be trimmed.

Explicit Semantic Role

The explicit semantic role of an element is determined by its role attribute (if any).

The role attribute takes a list of tokens. The explicit semantic role is the first valid role in this list. The valid roles are all non-abstract roles from WAI-ARIA Specifications. If the element has no role attribute, or if it has one with no valid role, then this element has no explicit semantic role.

Other roles may be added as they become available. Not all roles will be supported in all assistive technologies. Testers are encouraged to adjust which roles are allowed according to the accessibility support base line. For the purposes of executing test cases in all rules, it should be assumed that all roles are supported by assistive technologies so that none of the roles fail due to lack of accessibility support.

Focusable

An element is focusable if one or both of the following are true:

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

Form Field Error Indicator

Any text, or non-text content, or an element that has presentation indicating that an error was identified which appears to be related to some user input into, or the lack of user input into some element. These could be different types of errors, for example:

Note: An error indicator can be a separate element in the page, but it can also be part of a form control. For example a red outline on a form control is often used to indicate an error. Not all red outlines are indicators of an error though. This depends on the presentation of the form control in relation to other elements on the page.

Implicit Semantic Role

The implicit semantic role of an element is a pre-defined value given by the host language which depends on the element and its ancestors.

Implicit roles for HTML and SVG, are documented in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs are exposed to assistive technologies. This allows users of assistive technology to access the elements in a way that meets the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

For more details, see examples of included in the accessibility tree.

Programmatically hidden elements are removed from the accessibility tree. However, some browsers will leave focusable elements with an aria-hidden attribute set to true in the accessibility tree. Because they are hidden, these elements are considered not included in the accessibility tree. This may cause confusion for users of assistive technologies because they may still be able to interact with these focusable elements using sequential keyboard navigation, even though the element should not be included in the accessibility tree.

Marked as decorative

An element is marked as decorative if one or more of the following conditions is true:

Elements are marked as decorative as a way to convey the intention of the author that they are pure decoration. It is different from the element actually being pure decoration as authors may make mistakes. It is different from the element being effectively ignored by assistive technologies as rules such as presentational roles conflict resolution may overwrite this intention.

Elements can also be ignored by assistive technologies if they are programmatically hidden. This is different from marking the element as decorative and does not convey the same intention. Notably, being programmatically hidden may change as users interact with the page (showing and hiding elements) while being marked as decorative should stay the same through all states of the page.

Namespaced Element

An element with a specific namespaceURI value from HTML namespaces. For example an “SVG element” is any element with the “SVG namespace”, which is http://www.w3.org/2000/svg.

Namespaced elements are not limited to elements described in a specification. They also include custom elements. Elements such as a and title have a different namespace depending on where they are used. For example a title in an HTML page usually has the HTML namespace. When used in an svg element, a title element has the SVG namespace instead.

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.

Programmatically Hidden

An HTML element is programmatically hidden if either it has a computed CSS property visibility whose value is not visible; or at least one of the following is true for any of its inclusive ancestors in the flat tree:

Note: Contrarily to the other conditions, the visibility CSS property may be reverted by descendants.

Note: The HTML standard suggests rendering elements with the hidden attribute with a CSS rule that applies the value none to the CSS property display of the element. Although the suggestion is not normative, known user agents render it according to the suggestion (unless the content specifies another CSS rule that sets the value of the display property). If a user agent does not follow the suggestion, this definition may produce incorrect results for this user agent.

Semantic Role

The semantic role of an element is determined by the first of these cases that applies:

  1. Conflict If the element is marked as decorative, but the element is included in the accessibility tree; or would be included in the accessibility tree when it is not programmatically hidden, then its semantic role is its implicit role.
  2. Explicit If the element has an explicit role, then its semantic role is its explicit role.
  3. Implicit The semantic role of the element is its implicit role.

This definition can be used in expressions such as “semantic button” meaning any element with a semantic role of button.

Visible

Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

WAI-ARIA specifications

The WAI ARIA Specifications group both the WAI ARIA W3C Recommendation and ARIA modules, namely:

Note: depending on the type of content being evaluated, part of the specifications might be irrelevant and should be ignored.

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.

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This is an unpublished draft preview that might include content that is not yet approved. The published website is at w3.org/WAI/.