1 files changed, 76 insertions, 0 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 );
+	}
+}