2 files changed, 82 insertions, 4 deletions

diff --git a/tests/test-adjacent-post-order.php b/tests/test-adjacent-post-order.php
new file mode 100644
index 0000000..80939cf
--- /dev/null
+++ b/tests/test-adjacent-post-order.php
@@ -0,0 +1,76 @@
+<?php
+/**
+ * Class TestAdjacentPostOrder
+ *
+ * @package DraggablePostOrder
+ */
+
+use Draggable_Post_Order\Draggable_Post_Order;
+
+/**
+ * Sample test case.
+ */
+class TestAdjacentPostOrder extends WP_UnitTestCase {
+
+	/**
+	 * An array of posts for testing.
+	 *
+	 * @var WP_Post[]
+	 */
+	public array $test_posts = [];
+
+	/**
+	 * Runs the routine before each test is executed.
+	 */
+	public function setUp(): void {
+		parent::setUp();
+
+		add_post_type_support( 'post', Draggable_Post_Order::$post_type_feature );
+
+		// create three posts with order.
+		for ( $i = 1; $i <= 3; $i++ ) {
+			$id = $this->factory()->post->create();
+			update_post_meta( $id, Draggable_Post_Order::$meta_key, $i );
+
+			$this->test_posts[] = get_post( $id );
+		}
+
+		// since tests are loaded after init, run init manually.
+		Draggable_Post_Order::init();
+	}
+
+	/**
+	 * Test previous and next post with creation order
+	 */
+	public function test_previous_next_post_creation_order() {
+		$first  = $this->test_posts[0];
+		$second = $this->test_posts[1];
+		$third  = $this->test_posts[2];
+
+		$this->go_to( '/?p=' . $second->ID );
+
+		$this->assertEquals( $first->ID, get_previous_post()->ID );
+		$this->assertEquals( $third->ID, get_next_post()->ID );
+	}
+
+	/**
+	 * Test previous and next post jumbled order
+	 */
+	public function test_previous_next_post_jumbled_order() {
+		$first  = $this->test_posts[1];
+		$second = $this->test_posts[2];
+		$third  = $this->test_posts[0];
+
+		update_post_meta( $first->ID, Draggable_Post_Order::$meta_key, 1 );
+		update_post_meta( $second->ID, Draggable_Post_Order::$meta_key, 2 );
+		update_post_meta( $third->ID, Draggable_Post_Order::$meta_key, 3 );
+
+		// test whether the key was set properly.
+		$this->assertEquals( 2, get_post_meta( $second->ID, Draggable_Post_Order::$meta_key, true ) );
+
+		$this->go_to( '/?p=' . $second->ID );
+
+		$this->assertEquals( $first->ID, get_previous_post()->ID );
+		$this->assertEquals( $third->ID, get_next_post()->ID );
+	}
+}
diff --git a/tests/test-post-order.php b/tests/test-post-order.php
index b5b26c7..7aa0be4 100644
--- a/tests/test-post-order.php
+++ b/tests/test-post-order.php
@@ -5,6 +5,8 @@
  * @package DraggablePostOrder
  */
 
+use Draggable_Post_Order\Draggable_Post_Order;
+
 /**
  * Sample test case.
  */
@@ -26,13 +28,13 @@ class TestPostOrder extends WP_UnitTestCase {
 		$this->test_post_type = register_post_type(
 			'test',
 			[
-				'supports'    => [ 'draggable-post-order' ],
+				'supports'    => [ Draggable_Post_Order::$post_type_feature ],
 				'has_archive' => true,
 			]
 		);
 
 		// since tests are loaded after init, run init manually.
-		\Draggable_Post_Order\Draggable_Post_Order::init();
+		Draggable_Post_Order::init();
 	}
 
 	/**
@@ -45,12 +47,12 @@ class TestPostOrder extends WP_UnitTestCase {
 		$meta_sub_query = [
 			'relation'                           => 'OR',
 			'draggable-post-order-clause'        => [
-				'key'  => 'draggable-post-order',
+				'key'  => Draggable_Post_Order::$meta_key,
 				'type' => 'NUMERIC',
 			],
 			// get all posts without the meta as well.
 			'draggable-post-order-exists-clause' => [
-				'key'     => 'draggable-post-order',
+				'key'     => Draggable_Post_Order::$meta_key,
 				'compare' => 'NOT EXISTS',
 			],
 		];