diff --git a/phpunit/block-supports/position-test.php b/phpunit/block-supports/position-test.php
new file mode 100644
index 00000000000000..67bebc0bed5478
--- /dev/null
+++ b/phpunit/block-supports/position-test.php
@@ -0,0 +1,172 @@
+<?php
+
+/**
+ * Test the position block support.
+ *
+ * @package Gutenberg
+ */
+
+class WP_Block_Supports_Position_Test extends WP_UnitTestCase {
+	/**
+	 * @var string|null
+	 */
+	private $test_block_name;
+
+	/**
+	 * Theme root directory.
+	 *
+	 * @var string
+	 */
+	private $theme_root;
+
+	/**
+	 * Original theme directory.
+	 *
+	 * @var string
+	 */
+	private $orig_theme_dir;
+
+	public function set_up() {
+		parent::set_up();
+		$this->test_block_name = null;
+		$this->theme_root      = realpath( __DIR__ . '/../data/themedir1' );
+		$this->orig_theme_dir  = $GLOBALS['wp_theme_directories'];
+
+		// /themes is necessary as theme.php functions assume /themes is the root if there is only one root.
+		$GLOBALS['wp_theme_directories'] = array( WP_CONTENT_DIR . '/themes', $this->theme_root );
+
+		add_filter( 'theme_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'stylesheet_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'template_root', array( $this, 'filter_set_theme_root' ) );
+		// Clear caches.
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+	}
+
+	public function tear_down() {
+		$GLOBALS['wp_theme_directories'] = $this->orig_theme_dir;
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+		WP_Style_Engine_CSS_Rules_Store_Gutenberg::remove_all_stores();
+		unregister_block_type( $this->test_block_name );
+		$this->test_block_name = null;
+		parent::tear_down();
+	}
+
+	public function filter_set_theme_root() {
+		return $this->theme_root;
+	}
+
+	/**
+	 * Tests that position block support works as expected.
+	 *
+	 * @covers ::gutenberg_render_position_support
+	 *
+	 * @dataProvider data_position_block_support
+	 *
+	 * @param string $theme_name        The theme to switch to.
+	 * @param string $block_name        The test block name to register.
+	 * @param mixed  $position_settings The position block support settings.
+	 * @param mixed  $position_style    The position styles within the block attributes.
+	 * @param string $expected_wrapper  Expected markup for the block wrapper.
+	 * @param string $expected_styles   Expected styles enqueued by the style engine.
+	 */
+	public function test_position_block_support( $theme_name, $block_name, $position_settings, $position_style, $expected_wrapper, $expected_styles ) {
+		switch_theme( $theme_name );
+		$this->test_block_name = $block_name;
+
+		register_block_type(
+			$this->test_block_name,
+			array(
+				'api_version' => 2,
+				'attributes'  => array(
+					'style' => array(
+						'type' => 'object',
+					),
+				),
+				'supports'    => array(
+					'position' => $position_settings,
+				),
+			)
+		);
+
+		$block = array(
+			'blockName' => 'test/position-rules-are-output',
+			'attrs'     => array(
+				'style' => array(
+					'position' => $position_style,
+				),
+			),
+		);
+
+		$actual = gutenberg_render_position_support( '<div>Content</div>', $block );
+
+		$this->assertMatchesRegularExpression(
+			$expected_wrapper,
+			$actual,
+			'Position block wrapper markup should be correct'
+		);
+
+		$actual_stylesheet = gutenberg_style_engine_get_stylesheet_from_context( 'block-supports' );
+
+		$this->assertMatchesRegularExpression(
+			$expected_styles,
+			$actual_stylesheet,
+			'Position style rules output should be correct'
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function data_position_block_support() {
+		return array(
+			'sticky position style is applied' => array(
+				'theme_name'        => 'block-theme-child-with-fluid-typography',
+				'block_name'        => 'test/position-rules-are-output',
+				'position_settings' => true,
+				'position_style'    => array(
+					'type' => 'sticky',
+					'top'  => '0px',
+				),
+				'expected_wrapper'  => '/^<div class="wp-container-\d+">Content<\/div>$/',
+				'expected_styles'   => '/^.wp-container-\d+' . preg_quote( '{top:calc(0px + var(--wp-admin--admin-bar--height, 0px));position:sticky;z-index:10;}' ) . '$/',
+			),
+			'sticky position style is not applied if theme does not support it' => array(
+				'theme_name'        => 'default',
+				'block_name'        => 'test/position-rules-without-theme-support',
+				'position_settings' => true,
+				'position_style'    => array(
+					'type' => 'sticky',
+					'top'  => '0px',
+				),
+				'expected_wrapper'  => '/^<div>Content<\/div>$/',
+				'expected_styles'   => '/^$/',
+			),
+			'sticky position style is not applied if block does not support it' => array(
+				'theme_name'        => 'block-theme-child-with-fluid-typography',
+				'block_name'        => 'test/position-rules-without-block-support',
+				'position_settings' => false,
+				'position_style'    => array(
+					'type' => 'sticky',
+					'top'  => '0px',
+				),
+				'expected_wrapper'  => '/^<div>Content<\/div>$/',
+				'expected_styles'   => '/^$/',
+			),
+			'sticky position style is not applied if type is not valid' => array(
+				'theme_name'        => 'block-theme-child-with-fluid-typography',
+				'block_name'        => 'test/position-rules-with-valid-type',
+				'position_settings' => true,
+				'position_style'    => array(
+					'type' => 'illegal-type',
+					'top'  => '0px',
+				),
+				'expected_wrapper'  => '/^<div>Content<\/div>$/',
+				'expected_styles'   => '/^$/',
+			),
+		);
+	}
+}