diff --git a/tests/unit/data/ar/mongo/Customer.php b/tests/unit/data/ar/mongo/Customer.php
index 16819ca..83c4255 100644
--- a/tests/unit/data/ar/mongo/Customer.php
+++ b/tests/unit/data/ar/mongo/Customer.php
@@ -24,4 +24,9 @@ class Customer extends ActiveRecord
 	{
 		$query->andWhere(['status' => 2]);
 	}
+
+	public function getOrders()
+	{
+		return $this->hasMany(CustomerOrder::className(), ['customer_id' => 'id']);
+	}
 }
\ No newline at end of file
diff --git a/tests/unit/data/ar/mongo/CustomerOrder.php b/tests/unit/data/ar/mongo/CustomerOrder.php
new file mode 100644
index 0000000..2192be3
--- /dev/null
+++ b/tests/unit/data/ar/mongo/CustomerOrder.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace yiiunit\data\ar\mongo;
+
+
+class CustomerOrder extends ActiveRecord
+{
+	public static function collectionName()
+	{
+		return 'customer_order';
+	}
+
+	public function attributes()
+	{
+		return [
+			'_id',
+			'number',
+			'customer_id',
+			'items',
+		];
+	}
+
+	public function getCustomer()
+	{
+		return $this->hasOne(Customer::className(), ['id' => 'customer_id']);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/ActiveRelationTest.php b/tests/unit/extensions/mongo/ActiveRelationTest.php
new file mode 100644
index 0000000..ae12d72
--- /dev/null
+++ b/tests/unit/extensions/mongo/ActiveRelationTest.php
@@ -0,0 +1,83 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yiiunit\data\ar\mongo\ActiveRecord;
+use yiiunit\data\ar\mongo\Customer;
+use yiiunit\data\ar\mongo\CustomerOrder;
+
+/**
+ * @group mongo
+ */
+class ActiveRelationTest extends MongoTestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		ActiveRecord::$db = $this->getConnection();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropCollection(Customer::collectionName());
+		$this->dropCollection(CustomerOrder::collectionName());
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$customerCollection = $this->getConnection()->getCollection('customer');
+
+		$customers = [];
+		for ($i = 1; $i <= 5; $i++) {
+			$customers[] = [
+				'name' => 'name' . $i,
+				'email' => 'email' . $i,
+				'address' => 'address' . $i,
+				'status' => $i,
+			];
+		}
+		$customerCollection->batchInsert($customers);
+
+		$customerOrderCollection = $this->getConnection()->getCollection('customer_order');
+		$customerOrders = [];
+		foreach ($customers as $customer) {
+			$customerOrders[] = [
+				'customer_id' => $customer['_id'],
+				'number' => $customer['status'],
+			];
+			$customerOrders[] = [
+				'customer_id' => $customer['_id'],
+				'number' => $customer['status'] + 1,
+			];
+		}
+		$customerOrderCollection->batchInsert($customerOrders);
+	}
+
+	// Tests :
+
+	public function testFindLazy()
+	{
+		/** @var CustomerOrder $order */
+		$order = CustomerOrder::find(['number' => 2]);
+		$this->assertFalse($order->isRelationPopulated('customer'));
+		$index = $order->customer;
+		$this->assertTrue($order->isRelationPopulated('customer'));
+		$this->assertTrue($index instanceof Customer);
+		$this->assertEquals(1, count($order->populatedRelations));
+	}
+
+	public function testFindEager()
+	{
+		$orders = CustomerOrder::find()->with('customer')->all();
+		$this->assertEquals(10, count($orders));
+		$this->assertTrue($orders[0]->isRelationPopulated('customer'));
+		$this->assertTrue($orders[1]->isRelationPopulated('customer'));
+		$this->assertTrue($orders[0]->index instanceof ArticleIndex);
+		$this->assertTrue($orders[1]->index instanceof ArticleIndex);
+	}
+}
\ No newline at end of file