diff --git a/includes/gateway/traits/charge-request-builder.php b/includes/gateway/traits/charge-request-builder.php
index 1d5fe43b..3cdf0c3e 100644
--- a/includes/gateway/traits/charge-request-builder.php
+++ b/includes/gateway/traits/charge-request-builder.php
@@ -11,11 +11,7 @@ public function build_charge_request(
 	{
 		$currency = $order->get_currency();
 		$return_uri = $this->getRedirectUrl($callback_endpoint, $order_id, $order);
-		$description = apply_filters(
-			'omise_charge_params_description',
-			'WooCommerce Order id ' . $order_id,
-			$order
-		);
+		$description = 'WooCommerce Order id ' . $order_id;
 
 		return [
 			'amount'      => Omise_Money::to_subunit($order->get_total(), $currency),
@@ -38,12 +34,7 @@ public function getMetadata($order_id, $order, $additionalData = [])
 		// override order_id as a reference for webhook handlers.
 		$orderId = [ 'order_id' => $order_id ];
 
-		echo var_dump(apply_filters('omise_charge_params_metadata', [], $order));
-
-		return array_merge(
-			apply_filters('omise_charge_params_metadata', [], $order),
-			array_merge($orderId, $additionalData)
-		);
+		return array_merge($orderId, $additionalData);
 	}
 
 	/**
diff --git a/tests/unit/includes/gateway/class-omise-payment-ocbc-digital-test.php b/tests/unit/includes/gateway/class-omise-payment-ocbc-digital-test.php
index 54fd8e75..2370cfa3 100644
--- a/tests/unit/includes/gateway/class-omise-payment-ocbc-digital-test.php
+++ b/tests/unit/includes/gateway/class-omise-payment-ocbc-digital-test.php
@@ -12,6 +12,25 @@ public function setUp(): void
         require_once __DIR__ . '/../../../../includes/gateway/class-omise-payment-ocbc-digital.php';
         require_once __DIR__ . '/../../../../includes/classes/class-omise-image.php';
         $this->obj = new Omise_Payment_OCBC_Digital();
+
+        // mocking WP built-in functions
+        if (!function_exists('plugins_url')) {
+            function plugins_url() {
+                return "http://localhost";
+            }
+        }
+
+        if (!function_exists('apply_filters')) {
+            function apply_filters() {
+                return "http://localhost/image.png";
+            }
+        }
+
+        if (!function_exists('wc_get_user_agent')) {
+            function wc_get_user_agent() {
+                return "Chrome Web";
+            }
+        }
     }
 
     public function tearDown(): void
@@ -59,21 +78,7 @@ public function supportsIsCorrect()
      */
     public function getIconReturnsCorrectImageLink()
     {
-        // mocking WP built-in functions
-        if (!function_exists('plugins_url')) {
-            function plugins_url() {
-                return "http://localhost";
-            }
-        }
-
-        if (!function_exists('apply_filters')) {
-            function apply_filters() {
-                return "http://localhost/image.png";
-            }
-        }
-
         $result = $this->obj->get_icon();
-
         $this->assertEquals("http://localhost/image.png", $result);
     }
 
@@ -106,13 +111,6 @@ public function testCharge()
         $orderMock->shouldReceive('get_total')
             ->andReturn($expectedAmount/100);  // in units
 
-        if (!function_exists('wc_get_user_agent')) {
-            function wc_get_user_agent() {
-                return "Chrome Web";
-            }
-        }
-
-        $expectedSourceType = 'mobile_banking_ocbc';
         $order_id = "123";
         $result = $this->obj->charge($order_id, $orderMock);
         $this->assertEquals($expectedAmount, $result['amount']);
diff --git a/tests/unit/includes/gateway/traits/charge-request-builder-test.php b/tests/unit/includes/gateway/traits/charge-request-builder-test.php
index 2390ac7c..5935ca47 100644
--- a/tests/unit/includes/gateway/traits/charge-request-builder-test.php
+++ b/tests/unit/includes/gateway/traits/charge-request-builder-test.php
@@ -14,6 +14,12 @@ public static function setUpBeforeClass(): void
      */
     public function buildChargeRequestReturnsValidResponse()
     {
+        if (!function_exists('get_rest_url')) {
+            function get_rest_url() {
+                return "http://localhost/";
+            }
+        }
+
         $mock = $this->getMockForTrait('Charge_Request_Builder');
         $redirectUrlMock = Mockery::mock('alias:RedirectUrl');
         $redirectUrlMock->shouldReceive('create')
@@ -38,14 +44,6 @@ public function add_meta_data() {}
         $source_type = 'alipay';
         $callback_url = 'omise_alipay_callback';
 
-        // removed function_exists('apply_filters') check because "apply_filters"
-        // returns different data type such as string or array depending how it's
-        // implemented. So, even if "apply_filters" is already declared somewhere,
-        // it might not return the desired result. So, we are overriding it.
-        function apply_filters() {
-            return [];
-        }
-
         $result = $mock->build_charge_request(
             $order_id,
             $order,