添加PyQt GUI自动化测试套件

新增5个GUI测试模块，覆盖所有主要功能：
- test_login_gui.py: 登录和密码管理测试（7个测试）
- test_stock_gui.py: 库存管理测试（4个测试）
- test_raw_material_gui.py: 原料管理测试（7个测试）
- test_garment_gui.py: 款式管理测试（2个测试）
- test_purchase_order_gui.py: 采购单生成测试（2个测试）

测试特点：
- 真实GUI交互测试（填写表单、点击按钮、搜索过滤）
- 业务逻辑验证（重复数据拒绝、空值验证、计算正确性）
- 独立测试环境（临时数据库，自动清理）
- 自动化消息框（Mock QMessageBox）

总计22个GUI测试，全部通过 ✓

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

test/test_purchase_order.py

@@ -0,0 +1,111 @@
+"""
+采购单生成模块测试 - 测试采购单生成和计算功能
+"""
+
+import unittest
+import os
+import tempfile
+import gc
+from database import DatabaseManager, get_db_connection
+
+
+class TestPurchaseOrder(unittest.TestCase):
+    """采购单测试类"""
+
+    def setUp(self):
+        self.temp_dir = tempfile.mkdtemp()
+        self.db_path = os.path.join(self.temp_dir, "test_po.db")
+        self.db_manager = DatabaseManager(self.db_path)
+        self.conn = None
+        self._setup_test_data()
+
+    def tearDown(self):
+        if self.conn:
+            try:
+                self.conn.close()
+            except:
+                pass
+        gc.collect()
+        try:
+            if os.path.exists(self.db_path):
+                os.remove(self.db_path)
+            if os.path.exists(self.temp_dir):
+                os.rmdir(self.temp_dir)
+        except:
+            pass
+
+    def get_conn(self):
+        self.conn = get_db_connection(self.db_path)
+        return self.conn
+
+    def _setup_test_data(self):
+        """准备测试数据"""
+        with get_db_connection(self.db_path) as conn:
+            conn.execute(
+                "INSERT INTO garments (style_number) VALUES (?)",
+                ("PO-001",)
+            )
+            conn.execute('''
+                INSERT INTO garment_materials 
+                (style_number, category, model, usage_per_piece, unit)
+                VALUES (?, ?, ?, ?, ?)
+            ''', ("PO-001", "A料", "M001", 0.5, "米"))
+            conn.execute('''
+                INSERT INTO garment_materials 
+                (style_number, category, model, usage_per_piece, unit)
+                VALUES (?, ?, ?, ?, ?)
+            ''', ("PO-001", "B料", "M002", 0.3, "米"))
+            conn.commit()
+
+    def test_get_materials_for_style(self):
+        """测试获取款式材料"""
+        with self.get_conn() as conn:
+            cursor = conn.execute('''
+                SELECT category, model, usage_per_piece, unit
+                FROM garment_materials
+                WHERE style_number = ? AND usage_per_piece > 0
+                ORDER BY id
+            ''', ("PO-001",))
+            rows = cursor.fetchall()
+        self.assertEqual(len(rows), 2)
+        self.assertEqual(rows[0][0], "A料")
+        self.assertEqual(rows[1][0], "B料")
+
+    def test_calculate_total_usage(self):
+        """测试计算总用量"""
+        usage_per_piece = 0.5
+        quantity = 100
+        loss_rate = 0.05
+        total = usage_per_piece * quantity * (1 + loss_rate)
+        self.assertEqual(total, 52.5)
+
+    def test_calculate_total_usage_no_loss(self):
+        """测试无损耗计算"""
+        usage_per_piece = 0.5
+        quantity = 100
+        loss_rate = 0.0
+        total = usage_per_piece * quantity * (1 + loss_rate)
+        self.assertEqual(total, 50.0)
+
+    def test_calculate_total_usage_high_loss(self):
+        """测试高损耗计算"""
+        usage_per_piece = 0.5
+        quantity = 100
+        loss_rate = 0.10
+        total = usage_per_piece * quantity * (1 + loss_rate)
+        self.assertAlmostEqual(total, 55.0, places=2)
+
+    def test_empty_style_materials(self):
+        """测试空款式材料"""
+        with self.get_conn() as conn:
+            cursor = conn.execute('''
+                SELECT category, model, usage_per_piece, unit
+                FROM garment_materials
+                WHERE style_number = ? AND usage_per_piece > 0
+            ''', ("NOT-EXIST",))
+            rows = cursor.fetchall()
+        self.assertEqual(len(rows), 0)
+
+
+if __name__ == "__main__":
+    unittest.main()