Add tests

tests/cypress/integration/features/instant-results.cy.js

@@ -468,5 +468,30 @@ describe('Instant Results Feature', { tags: '@slow' }, () => {
 			 */
 			cy.get('.ep-search-sort :selected').should('contain.text', 'Date, newest to oldest');
 		});
+
+		it('Is possible to filter the taxonomy terms', () => {
+			/**
+			 * Activate test plugin.
+			 */
+			cy.maybeEnableFeature('instant-results');
+			cy.activatePlugin('filter-instant-results-facet-terms', 'wpCli');
+
+			/**
+			 * Perform a search.
+			 */
+			cy.intercept('*search=block*').as('apiRequest');
+			cy.visit('/');
+			cy.get('.wp-block-search').last().as('searchBlock');
+			cy.get('@searchBlock').find('input[type="search"]').type('block');
+			cy.get('@searchBlock').find('button').click();
+			cy.wait('@apiRequest');
+
+			/**
+			 * The number of terms displayed in the facet should be one.
+			 */
+			cy.get('[id^="ep-search-tax-category-"]').should('have.length', 1);
+
+			cy.deactivatePlugin('filter-instant-results-facet-terms', 'wpCli');
+		});
 	});
 });

tests/cypress/wordpress-files/test-plugins/filter-instant-results-facet-terms.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * Plugin Name: Filter Instant Results Taxonomy Terms
+ * Description: Filters the Instant Results taxonomy terms for test purposes.
+ * Version:     1.0.0
+ * Author:      10up Inc.
+ * License:     GPLv2 or later
+ *
+ * @package ElasticPress_Tests_E2e
+ */
+
+/**
+ * Limit the Instant Results facet terms to only the "Classic" term.
+ */
+add_action(
+	'wp_footer',
+	function (): void {
+		?>
+		<script>
+			document.addEventListener('DOMContentLoaded', function() {
+				const filterCategoryTerms = (terms, taxonomyName) => {
+
+					if (taxonomyName !== 'tax-category') {
+						return terms;
+					}
+
+					// keep only Term Classic
+					const filteredTerms = terms.filter(term => term.label === 'Classic');
+					return filteredTerms;
+				}
+
+				wp.hooks.addFilter('ep.InstantResults.facet.taxonomy.terms', 'ep-test', filterCategoryTerms);
+			});
+		</script>
+		<?php
+	}
+);