diff --git a/pyproject.toml b/pyproject.toml
index 43bc952..84ae486 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "usf"
-version = "0.1.2"
+version = "0.2.0"
 description = "A lightweight Universal Schedule Format (USF) parser and generator."
 authors = [{ name = "USF-org", email = "USF-org@outlook.com" }]
 license = { text = "MIT" }
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..751f60a
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+jsonschema==4.0.0
\ No newline at end of file
diff --git a/setup.py b/setup.py
index 43ef90f..feaf578 100644
--- a/setup.py
+++ b/setup.py
@@ -2,7 +2,7 @@
 
 setup(
     name="usf",
-    version="0.1.2",
+    version="0.2.0",
     packages=find_packages(),
     install_requires=[],
     python_requires=">=3.6",
diff --git a/tests/test_usf.py b/tests/test_usf.py
index dc37018..69941aa 100644
--- a/tests/test_usf.py
+++ b/tests/test_usf.py
@@ -22,7 +22,7 @@ def setUp(self):
         self.generator.add_schedule(1, "all", "Physics", 2)      # 星期一，第二节，物理
 
         # 生成 USF 数据
-        self.usf_data = self.generator.generate_usf_data()
+        self.usf_data = self.generator.generate()
 
     def test_usf_generation(self):
         """测试 USF 生成"""
@@ -38,7 +38,10 @@ def test_usf_generation(self):
 
     def test_usf_parser(self):
         """测试 USF 解析"""
+        # 将生成的 USF 数据转为 JSON 字符串
         json_data = json.dumps(self.usf_data, indent=2)
+
+        # 使用解析器解析数据
         parser = USFParser(json_data)
 
         self.assertEqual(len(parser.get_subjects()), 2)
@@ -63,7 +66,38 @@ def test_usf_validation(self):
             "subjects": self.usf_data["subjects"],
             "periods": self.usf_data["periods"]
         }
-        self.assertFalse(validator.validate(invalid_data))
+
+        # 这里我们添加了额外的错误处理来捕获无效数据的校验错误
+        with self.assertRaises(jsonschema.exceptions.ValidationError):
+            validator.validate(invalid_data)
+
+    def test_invalid_period(self):
+        """测试无效时间段"""
+        invalid_periods_data = {
+            "version": 1,
+            "subjects": self.usf_data["subjects"],
+            "periods": [["invalid", "format"]],
+            "timetable": self.usf_data["timetable"]
+        }
+        
+        # 使用校验器验证无效的时间段数据
+        validator = USFValidator()
+        with self.assertRaises(jsonschema.exceptions.ValidationError):
+            validator.validate(invalid_periods_data)
+
+    def test_invalid_subject(self):
+        """测试无效科目"""
+        invalid_subjects_data = {
+            "version": 1,
+            "subjects": {"InvalidSubject": {}},
+            "periods": self.usf_data["periods"],
+            "timetable": self.usf_data["timetable"]
+        }
+
+        # 使用校验器验证无效的科目数据
+        validator = USFValidator()
+        with self.assertRaises(jsonschema.exceptions.ValidationError):
+            validator.validate(invalid_subjects_data)
 
 if __name__ == "__main__":
     unittest.main()
\ No newline at end of file
diff --git a/usf/generator.py b/usf/generator.py
index 3afd15d..91ad2d0 100644
--- a/usf/generator.py
+++ b/usf/generator.py
@@ -1,4 +1,5 @@
 import json
+import re
 
 class USFGenerator:
     def __init__(self, version=1):
@@ -23,6 +24,9 @@ def add_subject(self, name, simplified_name=None, teacher=None, room=None):
             teacher (str, optional): Teacher's name.
             room (str, optional): Classroom.
         """
+        if name in self.subjects:
+            raise ValueError(f"Subject '{name}' already exists.")
+        
         self.subjects[name] = {
             "simplified_name": simplified_name or name,
             "teacher": teacher or "",
@@ -40,6 +44,10 @@ def add_period(self, start_time, end_time):
         Returns:
             int: Index of the added period (1-based).
         """
+        time_pattern = "^(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d$"
+        if not re.match(time_pattern, start_time) or not re.match(time_pattern, end_time):
+            raise ValueError(f"Invalid time format. Must be 'HH:MM:SS'.")
+
         self.periods.append([start_time, end_time])
         return len(self.periods)  # Return 1-based index
 
@@ -57,6 +65,9 @@ def add_schedule(self, day, week_type, subject, period_index):
             raise ValueError(f"Subject '{subject}' is not defined.")
         if period_index < 1 or period_index > len(self.periods):
             raise ValueError(f"Invalid period index {period_index}.")
+        if week_type not in ["all", "even", "odd"]:
+            raise ValueError(f"Invalid week type '{week_type}'. Must be 'all', 'even', or 'odd'.")
+        
         self.timetable.append([day, week_type, subject, period_index])
 
     def generate(self):
@@ -80,5 +91,8 @@ def save_to_file(self, filename):
         Args:
             filename (str): Output filename.
         """
-        with open(filename, "w", encoding="utf-8") as f:
-            json.dump(self.generate(), f, indent=2, ensure_ascii=False)
\ No newline at end of file
+        try:
+            with open(filename, "w", encoding="utf-8") as f:
+                json.dump(self.generate(), f, indent=2, ensure_ascii=False)
+        except Exception as e:
+            raise IOError(f"Failed to save USF data to {filename}: {e}")
\ No newline at end of file
diff --git a/usf/parser.py b/usf/parser.py
index 97665c0..ef18265 100644
--- a/usf/parser.py
+++ b/usf/parser.py
@@ -8,8 +8,13 @@ def __init__(self, filename):
         Args:
             filename (str): Path to USF JSON file.
         """
-        with open(filename, "r", encoding="utf-8") as f:
-            self.data = json.load(f)
+        try:
+            with open(filename, "r", encoding="utf-8") as f:
+                self.data = json.load(f)
+        except FileNotFoundError:
+            raise FileNotFoundError(f"File '{filename}' not found.")
+        except json.JSONDecodeError:
+            raise ValueError(f"Failed to decode JSON from the file '{filename}'.")
 
     def get_subjects(self):
         """Return the subjects dictionary."""
diff --git a/usf/validator.py b/usf/validator.py
index 7999982..c529873 100644
--- a/usf/validator.py
+++ b/usf/validator.py
@@ -10,8 +10,13 @@ def __init__(self, schema_file="schema.json"):
         Args:
             schema_file (str, optional): Path to JSON Schema. Defaults to "schema.json".
         """
-        with open(schema_file, "r", encoding="utf-8") as f:
-            self.schema = json.load(f)
+        try:
+            with open(schema_file, "r", encoding="utf-8") as f:
+                self.schema = json.load(f)
+        except FileNotFoundError:
+            raise FileNotFoundError(f"Schema file '{schema_file}' not found.")
+        except json.JSONDecodeError:
+            raise ValueError(f"Failed to decode JSON from the schema file '{schema_file}'.")
 
     def validate(self, data):
         """
@@ -23,6 +28,8 @@ def validate(self, data):
         Returns:
             bool: True if valid, raises an error if invalid.
         """
-        validate(instance=data, schema=self.schema)
-        return True
-    
\ No newline at end of file
+        try:
+            validate(instance=data, schema=self.schema)
+        except jsonschema.exceptions.ValidationError as e:
+            raise ValueError(f"USF data validation failed: {e.message}")
+        return True
\ No newline at end of file