Issue magento#35545 Add Unit tests

app/code/Magento/QuoteGraphQl/Test/Unit/Model/Resolver/DiscountsTest.php

@@ -0,0 +1,90 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\QuoteGraphQl\Test\Unit\Model\Resolver;
+
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+use Magento\GraphQl\Model\Query\Context;
+use Magento\QuoteGraphQl\Model\Resolver\Discounts;
+use PHPUnit\Framework\TestCase;
+use PHPUnit\Framework\MockObject\MockObject;
+
+/**
+ * @see Discounts
+ */
+class DiscountsTest extends TestCase
+{
+    /**
+     * @var Discounts
+     */
+    private Discounts $discounts;
+
+    /**
+     * @var Field|MockObject
+     */
+    private Field $fieldMock;
+
+    /**
+     * @var ResolveInfo|MockObject
+     */
+    private ResolveInfo $resolveInfoMock;
+
+    /**
+     * @var Context|MockObject
+     */
+    private Context $contextMock;
+
+    protected function setUp(): void
+    {
+        $this->fieldMock = $this->createMock(Field::class);
+        $this->resolveInfoMock = $this->createMock(ResolveInfo::class);
+        $this->contextMock = $this->createMock(Context::class);
+        $this->discounts = new Discounts();
+    }
+
+    /**
+     * @return array
+     */
+    public function dataProviderDiscounts(): array
+    {
+        return [[[
+            'discount' => [
+                'label' => ['Discount'],
+                'amount' => [
+                    'value' => 100,
+                    'currency' => 'USD'
+                ]
+            ]
+        ]]];
+    }
+
+    /**
+     * @dataProvider dataProviderDiscounts
+     */
+    public function testResolve(array $discount): void
+    {
+        $expected = [
+            [
+                'label' => __('Discount'),
+                'amount' => [
+                    'value' => 100,
+                    'currency' => 'USD'
+                ]
+            ]
+        ];
+
+        $result = $this->discounts->resolve(
+            $this->fieldMock,
+            $this->contextMock,
+            $this->resolveInfoMock,
+            $discount
+        );
+
+        $this->assertEquals($expected, $result);
+    }
+}