Unit Tests: Added test_add_discount method.

tests/unit-tests/cart.php

@@ -428,6 +428,31 @@ class WC_Tests_Cart extends WC_Unit_Test_Case {
 
 		$this->assertEquals( apply_filters( 'woocommerce_cart_needs_shipping_address', $needs_shipping_address ), WC()->cart->needs_shipping_address() );
 	}
-	
+
+	/**
+	 * DISCOUNT TESTS
+	 */
+
+	/**
+	 * Test add_discount method
+	 */
+	public function test_add_discount() {
+
+		// Create coupon
+		$coupon = WC_Helper_Coupon::create_coupon();
+
+		// Add coupon, test return statement
+		$this->assertTrue( WC()->cart->add_discount( $coupon->code ) );
+
+		// Test if total amount of coupons is 1
+		$this->assertEquals( 1, count( WC()->cart->get_applied_coupons() ) );
+
+		// Clean up the cart
+		WC()->cart->empty_cart();
+
+		// Delete coupon
+		WC_Helper_Coupon::delete_coupon( $coupon->id );
+
+	}
 
 }