diff --git a/packages/blocks/src/class-blocks.php b/packages/blocks/src/class-blocks.php
index 208707af45008..69b0d07b11172 100644
--- a/packages/blocks/src/class-blocks.php
+++ b/packages/blocks/src/class-blocks.php
@@ -17,7 +17,58 @@
  * @since 9.0.0
  */
 class Blocks {
+	/**
+	 * Get CSS classes for a block.
+	 *
+	 * @since 9.0.0
+	 *
+	 * @param string $slug  Block slug.
+	 * @param array  $attr  Block attributes.
+	 * @param array  $extra Potential extra classes you may want to provide.
+	 *
+	 * @return string $classes List of CSS classes for a block.
+	 */
+	public static function classes( $slug, $attr, $extra = array() ) {
+		if ( empty( $slug ) ) {
+			return '';
+		}
 
-}
+		// Basic block name class.
+		$classes = array(
+			'wp-block-jetpack-' . $slug,
+		);
+
+		// Add alignment if provided.
+		if (
+			! empty( $attr['align'] )
+			&& in_array( $attr['align'], array( 'left', 'center', 'right', 'wide', 'full' ), true )
+		) {
+			$classes[] = 'align' . $attr['align'];
+		}
+
+		// Add custom classes if provided in the block editor.
+		if ( ! empty( $attr['className'] ) ) {
+			$classes[] = $attr['className'];
+		}
+
+		// Add any extra classes.
+		if ( is_array( $extra ) && ! empty( $extra ) ) {
+			$classes = array_merge( $classes, array_filter( $extra ) );
+		}
 
+		return implode( ' ', $classes );
+	}
+
+	/**
+	 * Does the page return AMP content.
+	 *
+	 * @return bool $is_amp_request Are we on an AMP view.
+	 */
+	public static function is_amp_request() {
+		$is_amp_request = ( function_exists( 'is_amp_endpoint' ) && is_amp_endpoint() );
+
+		/** This filter is documented in 3rd-party/class.jetpack-amp-support.php */
+		return apply_filters( 'jetpack_is_amp_request', $is_amp_request );
+	}
+}
 
diff --git a/packages/blocks/tests/php/bootstrap.php b/packages/blocks/tests/php/bootstrap.php
new file mode 100644
index 0000000000000..9a50b9a7a6730
--- /dev/null
+++ b/packages/blocks/tests/php/bootstrap.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * PHPUnit bootstrap file.
+ *
+ * @package automattic/jetpack-blocks
+ */
+
+/**
+ * Load the composer autoloader.
+ */
+require_once __DIR__ . '/../../vendor/autoload.php';
+
+/**
+ * Load WorDBless
+ */
+\WorDBless\Load::load();
diff --git a/packages/blocks/tests/php/test-blocks.php b/packages/blocks/tests/php/test-blocks.php
new file mode 100644
index 0000000000000..464012699cc20
--- /dev/null
+++ b/packages/blocks/tests/php/test-blocks.php
@@ -0,0 +1,87 @@
+<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
+/**
+ * Test methods from Automattic\Jetpack\Blocks
+ *
+ * @since 9.0.0
+ *
+ * @package automattic/jetpack-blocks
+ */
+
+namespace Automattic\Jetpack;
+
+use Automattic\Jetpack\Blocks;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Class Test_Blocks
+ */
+class Test_Blocks extends TestCase {
+	/**
+	 * Test the different inputs and matching output for Classes.
+	 *
+	 * @since 9.0.0
+	 *
+	 * @covers Automattic\Jetpack\Blocks::classes
+	 */
+	public function test_block_classes() {
+		$block_name = 'foo';
+		$attr       = array(
+			'bar'       => 'baz',
+			'align'     => 'wide',
+			'className' => 'editorclass',
+		);
+		$extra      = array( 'extraclass' );
+
+		$block_classes = Blocks::classes( $block_name, $attr, $extra );
+
+		$this->assertContains( 'wp-block-jetpack-foo', $block_classes ); // a general class is created from the block name.
+		$this->assertNotContains( 'bar', $block_classes ); // The extra 'bar' attribute should be dropped.
+		$this->assertNotContains( 'baz', $block_classes ); // The extra 'baz' attribute should be dropped.
+		$this->assertNotContains( 'align ', $block_classes ); // The align attribute should only be used to create a new attribute.
+		$this->assertNotContains( 'className', $block_classes ); // The className attribute should be dropped, only the editorclass value should remain.
+		$this->assertContains( 'alignwide', $block_classes ); // an alignment class is created.
+		$this->assertContains( 'editorclass', $block_classes ); // className classes are passed.
+		$this->assertContains( 'extraclass', $block_classes ); // Extra class remains.
+	}
+
+	/**
+	 * Test for invalid alignment values.
+	 *
+	 * @since 9.0.0
+	 *
+	 * @covers Automattic\Jetpack\Blocks::classes
+	 */
+	public function test_block_classes_invalid_align() {
+		$attr          = array( 'align' => 'test' );
+		$block_classes = Blocks::classes( 'test', $attr );
+
+		$this->assertNotContains( 'aligntest', $block_classes );
+	}
+
+	/**
+	 * Test whether we can detect an AMP view.
+	 *
+	 * @since 9.0.0
+	 *
+	 * @covers Automattic\Jetpack\Blocks::is_amp_request
+	 */
+	public function test_is_amp_request() {
+		add_filter( 'jetpack_is_amp_request', '__return_true' );
+		try {
+			$this->assertTrue( Blocks::is_amp_request() );
+		} finally {
+			remove_filter( 'jetpack_is_amp_request', '__return_true' );
+		}
+	}
+
+	/**
+	 * Test whether we can detect an AMP view.
+	 *
+	 * @since 9.0.0
+	 *
+	 * @covers Automattic\Jetpack\Blocks::is_amp_request
+	 */
+	public function test_is_not_amp_request() {
+		$this->assertFalse( Blocks::is_amp_request() );
+	}
+}