diff --git a/tests/test_code_analyzer.py b/tests/test_code_analyzer.py
new file mode 100644
index 0000000..ee4ad4c
--- /dev/null
+++ b/tests/test_code_analyzer.py
@@ -0,0 +1,87 @@
+"""Tests for the CodeAnalyzer module."""
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent.parent / 'src'))
+
+from gdiffer.code_analyzer import CodeAnalyzer, analyze_code, summarize_change
+
+
+class TestCodeAnalyzer:
+    def test_analyze_empty_code(self, code_analyzer):
+        result = code_analyzer.analyze_code("")
+        assert result['language'] == "text"
+        assert result['change_summary'] == ""
+
+    def test_analyze_python_code(self, code_analyzer):
+        code = """def hello():
+    return "Hello"
+
+class Greeter:
+    def greet(self, name):
+        return f"Hello, {name}"
+"""
+        result = code_analyzer.analyze_code(code, "python")
+        assert result['language'] == "python"
+
+    def test_analyze_javascript_code(self, code_analyzer):
+        code = """function add(a, b) {
+    return a + b;
+}"""
+        result = code_analyzer.analyze_code(code, "javascript")
+        assert result['language'] == "javascript"
+
+    def test_summarize_change_simple(self, code_analyzer):
+        old_code = "def hello():\n    return 'Hello'"
+        new_code = "def hello():\n    return 'Hello, World!'"
+        summary = code_analyzer.summarize_change(old_code, new_code, "python")
+        assert isinstance(summary, str)
+        assert len(summary) > 0
+
+    def test_summarize_change_added_function(self, code_analyzer):
+        old_code = ""
+        new_code = "def new_func():\n    pass"
+        summary = code_analyzer.summarize_change(old_code, new_code, "python")
+        assert isinstance(summary, str)
+        assert len(summary) > 0
+
+    def test_analyze_code_without_parser(self, code_analyzer):
+        code = "def test(): pass"
+        result = code_analyzer.analyze_code(code, "unknown_language")
+        assert 'change_summary' in result
+
+    def test_fallback_analysis_detects_functions(self, code_analyzer):
+        code = """def calculate_sum(a, b):
+    return a + b
+
+def multiply(x, y):
+    return x * y
+"""
+        result = code_analyzer._analyze_without_parser(code)
+        assert isinstance(result, str)
+
+    def test_fallback_analysis_detects_classes(self, code_analyzer):
+        code = """class Calculator:
+    def add(self, a, b):
+        return a + b
+"""
+        result = code_analyzer._analyze_without_parser(code)
+        assert "Calculator" in result or "class" in result.lower()
+
+
+class TestAnalyzeCodeFunction:
+    def test_analyze_code_function(self):
+        result = analyze_code("def test(): pass", "python")
+        assert 'language' in result
+        assert 'change_summary' in result
+
+    def test_analyze_code_empty(self):
+        result = analyze_code("", "text")
+        assert result['language'] == "text"
+
+
+class TestSummarizeChangeFunction:
+    def test_summarize_change_function(self):
+        result = summarize_change("old", "new", "text")
+        assert isinstance(result, str)