Tests: Trim and reorganize icon collection tests.

Drop the redundant coverage cases that only assert trivial singleton,
getter, and wrapper behavior already exercised elsewhere, and relocate
the `data_invalid_collection_slugs` data provider next to its consumer
with a clarifying docblock.

Keeps the focus on the meaningful contract: validation failures,
duplicate registration, unknown-property rejection, and the cascading
unregister behavior.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: t-hamano

tests/phpunit/tests/icons/wpIconCollectionsRegistry.php

@@ -53,16 +53,6 @@ public function test_register_collection() {
 		$this->assertSame( 'A collection.', $registered['description'] );
 	}
 
-	public function data_invalid_collection_slugs() {
-		return array(
-			'non-string slug'      => array( 1 ),
-			'contains slash'       => array( 'plugin/icons' ),
-			'contains digits'      => array( 'plugin1' ),
-			'uppercase characters' => array( 'Plugin' ),
-			'leading hyphen'       => array( '-plugin' ),
-		);
-	}
-
 	/**
 	 * @ticket 64847
 	 *
@@ -80,15 +70,22 @@ public function test_register_rejects_invalid_slug( $slug ) {
 	}
 
 	/**
-	 * @ticket 64847
+	 * Data provider for invalid collection slug candidates.
 	 *
-	 * @covers ::register
+	 * Collection slugs must be strings that start with a lowercase letter
+	 * and contain only lowercase letters and hyphens (no digits, no slashes,
+	 * no uppercase characters).
 	 *
-	 * @expectedIncorrectUsage WP_Icon_Collections_Registry::register
+	 * @return array[]
 	 */
-	public function test_register_rejects_missing_label() {
-		$result = $this->collections->register( 'my-collection', array() );
-		$this->assertFalse( $result );
+	public function data_invalid_collection_slugs() {
+		return array(
+			'non-string slug'      => array( 1 ),
+			'contains slash'       => array( 'plugin/icons' ),
+			'contains digits'      => array( 'plugin1' ),
+			'uppercase characters' => array( 'Plugin' ),
+			'leading hyphen'       => array( '-plugin' ),
+		);
 	}
 
 	/**
@@ -178,80 +175,4 @@ public function test_unregister_collection_cascades_to_icons() {
 	public function test_unregister_unknown_collection() {
 		$this->assertFalse( $this->collections->unregister( 'ghost' ) );
 	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::get_all_registered
-	 */
-	public function test_get_all_registered_contains_core() {
-		$slugs = wp_list_pluck( $this->collections->get_all_registered(), 'slug' );
-		$this->assertContains( 'core', $slugs );
-	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::get_registered
-	 */
-	public function test_get_registered_returns_null_when_missing() {
-		$this->assertNull( $this->collections->get_registered( 'ghost' ) );
-	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::is_registered
-	 */
-	public function test_is_registered_on_default_core() {
-		$this->assertTrue( $this->collections->is_registered( 'core' ) );
-	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::get_instance
-	 */
-	public function test_get_instance_returns_singleton() {
-		$this->assertSame( $this->collections, WP_Icon_Collections_Registry::get_instance() );
-	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::register
-	 */
-	public function test_wp_register_icon_collection_wrapper() {
-		$this->assertTrue(
-			wp_register_icon_collection( 'my-collection', array( 'label' => 'My' ) )
-		);
-		$this->assertTrue( $this->collections->is_registered( 'my-collection' ) );
-
-		$this->assertTrue( wp_unregister_icon_collection( 'my-collection' ) );
-		$this->assertFalse( $this->collections->is_registered( 'my-collection' ) );
-	}
-
-	/**
-	 * @ticket 64847
-	 *
-	 * @covers ::register
-	 */
-	public function test_wp_register_icon_wrapper() {
-		wp_register_icon_collection( 'my-collection', array( 'label' => 'My' ) );
-
-		$this->assertTrue(
-			wp_register_icon(
-				'bell',
-				'my-collection',
-				array(
-					'label'   => 'Bell',
-					'content' => '<svg></svg>',
-				)
-			)
-		);
-		$this->assertTrue( WP_Icons_Registry::get_instance()->is_registered( 'my-collection/bell' ) );
-
-		$this->assertTrue( wp_unregister_icon( 'bell', 'my-collection' ) );
-		$this->assertFalse( WP_Icons_Registry::get_instance()->is_registered( 'my-collection/bell' ) );
-	}
 }