Axe runner doesn't include wcag2aaa tag when standard is set to WCAG2AAA.

[osimblahan]

Expected behaviour

Axe WCAG2AAA tagged tests should be included.

Actual behaviour

They are not. (Only three tests exist at this time.)

Tag is listed in the axe docs. (There is also the wcag22aa tag with one test, but that's not technically a standard yet.)
https://www.deque.com/axe/core-documentation/api-documentation/#api-notes

Steps to reproduce

Run pa11y with standard: 'WCAG2AAA' and the axe runner.

Problem area in runners/axe.js

function pa11yStandardToAxe() {
    switch (options.standard) {
        case 'WCAG2A':
            return {
                type: 'tags',
                values: ['wcag2a', 'wcag21a', 'best-practice']
            };
        case 'WCAG2AA':
        case 'WCAG2AAA':
        default:
            return {
                type: 'tags',
                values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'best-practice']
            };
    }
}

[camtin]

Since WCAG 2.2 is now the standard, I wonder if we should include WCAG 2.2.

Additionally, I wonder if we should "accept" options that are more like:

WCAG2A
WCAG21A
WCAG22A
WCAG2AA
WCAG21AA
WCAG22AA
WCAG2AAA
WCAG21AAA
WCAG22AAA

Or is there a specific reason Pa11y doesn't differentiate between the different revisions here?

[camtin]

Essentially, I think we want this (based on the available options from Axe core)
https://www.deque.com/axe/core-documentation/api-documentation/

This always includes best practices, and makes WCAG 2.2 AAA.

Unfortunately I think this is a breaking change though as WCAG2A now would map to WCAG 2.0 A for example, not WCAG 2.1 A anymore.

	/**
	 * Map the Pa11y standard option to the aXe runOnly option.
	 * @private
	 * @returns {RunOnly} Returns the aXe runOnly value.
	 */
	function pa11yStandardToAxe() {
		console.log("Scan Standard: "+options.standard);
		switch (options.standard) {
			case 'WCAG2A':
				return {
					type: 'tags',
					values: ['wcag2a','best-practice']
				};

			case 'WCAG2AA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag2aa', 'best-practice']
				};	

			case 'WCAG2AAA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag2aa', 'wcag2aaa', 'best-practice']
				};				

			case 'WCAG21A':
			case 'WCAG22A':				
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'best-practice']
				};	

			case 'WCAG21AA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'best-practice']
				};	

			case 'WCAG21AA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'wcag2aaa', 'best-practice']
				};

			case 'WCAG22AA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'wcag22aa', 'best-practice']
				};	

			case 'WCAG22AAA':
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'wcag22aa', 'wcag2aaa', 'best-practice']
				};	

			default:
				return {
					type: 'tags',
					values: ['wcag2a', 'wcag21a', 'wcag2aa', 'wcag21aa', 'wcag22aa', 'best-practice']
				};
		}
	}