Implement test coverage to ensure template part block works correctly…

… even without theme attribute.

tests/phpunit/tests/blocks/renderBlockCoreTemplatePart.php

@@ -0,0 +1,121 @@
+<?php
+/**
+ * Tests for `render_block_core_template_part()`.
+ *
+ * @package WordPress
+ * @subpackage Blocks
+ *
+ * @group blocks
+ */
+class Tests_Blocks_RenderBlockCoreTemplatePart extends WP_UnitTestCase {
+
+	/**
+	 * Temporary storage for original block to render.
+	 *
+	 * @var array|null
+	 */
+	private $original_block_to_render = null;
+
+	/**
+	 * Flag to indicate whether to switch back to the default theme at tear down.
+	 *
+	 * @var bool
+	 */
+	private $switch_to_default_theme_at_teardown = false;
+
+	public function set_up() {
+		parent::set_up();
+
+		$this->original_block_to_render = WP_Block_Supports::$block_to_render;
+	}
+
+	public function tear_down() {
+		WP_Block_Supports::$block_to_render = $this->original_block_to_render;
+		$this->original_block_to_render     = null;
+
+		if ( $this->switch_to_default_theme_at_teardown ) {
+			$this->switch_to_default_theme_at_teardown = false;
+			switch_theme( WP_DEFAULT_THEME );
+		}
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that the core template part block assumes the current theme if no theme attribute provided.
+	 *
+	 * @ticket 59583
+	 */
+	public function test_render_block_core_template_part_without_theme_attribute() {
+		$this->maybe_switch_theme( 'block-theme' );
+
+		WP_Block_Supports::$block_to_render = array( 'blockName' => 'core/template-part' );
+
+		$content = render_block_core_template_part( array( 'slug' => 'small-header' ) );
+
+		$expected  = '<header class="wp-block-template-part">' . "\n";
+		$expected .= '<p>Small Header Template Part</p>' . "\n";
+		$expected .= '</header>';
+
+		$this->assertSame( $expected, $content );
+	}
+
+	/**
+	 * Tests that the core template part block returns the relevant part if current theme attribute provided.
+	 *
+	 * @ticket 59583
+	 */
+	public function test_render_block_core_template_part_with_current_theme_attribute() {
+		$this->maybe_switch_theme( 'block-theme' );
+
+		WP_Block_Supports::$block_to_render = array( 'blockName' => 'core/template-part' );
+
+		$content = render_block_core_template_part(
+			array(
+				'slug'  => 'small-header',
+				'theme' => 'block-theme',
+			)
+		);
+
+		$expected  = '<header class="wp-block-template-part">' . "\n";
+		$expected .= '<p>Small Header Template Part</p>' . "\n";
+		$expected .= '</header>';
+
+		$this->assertSame( $expected, $content );
+	}
+
+	/**
+	 * Tests that the core template part block returns nothing if theme attribute for a different theme provided.
+	 *
+	 * @ticket 59583
+	 */
+	public function test_render_block_core_template_part_with_another_theme_attribute() {
+		$this->maybe_switch_theme( 'block-theme' );
+
+		WP_Block_Supports::$block_to_render = array( 'blockName' => 'core/template-part' );
+
+		$content = render_block_core_template_part(
+			array(
+				'slug'  => 'small-header',
+				'theme' => WP_DEFAULT_THEME,
+			)
+		);
+
+		$expected = 'Template part has been deleted or is unavailable: small-header';
+		$this->assertSame( $expected, $content );
+	}
+
+	/**
+	 * Switches the theme when not the default theme.
+	 *
+	 * @param string $theme Theme name to switch to.
+	 */
+	private function maybe_switch_theme( $theme ) {
+		if ( WP_DEFAULT_THEME === $theme ) {
+			return;
+		}
+
+		switch_theme( $theme );
+		$this->switch_to_default_theme_at_teardown = true;
+	}
+}