diff --git a/tests/test_parser.py b/tests/test_parser.py
new file mode 100644
index 0000000..0832037
--- /dev/null
+++ b/tests/test_parser.py
@@ -0,0 +1,144 @@
+"""Tests for OpenAPI Spec Parser."""
+
+import pytest
+from pathlib import Path
+
+from src.core.parser import (
+    OpenAPIParser,
+    OpenAPIParserError,
+    InvalidOpenAPIFormat,
+    UnsupportedOpenAPIVersion,
+)
+
+
+class TestOpenAPIParser:
+    """Tests for OpenAPIParser class."""
+
+    def test_load_valid_yaml_spec(self, temp_spec_file):
+        """Test loading a valid YAML OpenAPI specification."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        spec = parser.load()
+
+        assert spec is not None
+        assert spec["openapi"] == "3.0.0"
+        assert spec["info"]["title"] == "Sample API"
+        assert spec["info"]["version"] == "1.0.0"
+
+    def test_load_valid_json_spec(self, temp_json_spec_file):
+        """Test loading a valid JSON OpenAPI specification."""
+        parser = OpenAPIParser(str(temp_json_spec_file))
+        spec = parser.load()
+
+        assert spec is not None
+        assert spec["openapi"] == "3.0.0"
+
+    def test_file_not_found(self):
+        """Test handling of non-existent spec file."""
+        parser = OpenAPIParser("/nonexistent/path/openapi.yaml")
+
+        with pytest.raises(FileNotFoundError):
+            parser.load()
+
+    def test_get_paths(self, temp_spec_file):
+        """Test extracting paths from specification."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+        paths = parser.get_paths()
+
+        assert "/users" in paths
+        assert "/users/{userId}" in paths
+        assert "/posts" in paths
+
+    def test_get_response_schema(self, temp_spec_file):
+        """Test extracting response schema for an operation."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+
+        schema = parser.get_response_schema("/users", "get", "200")
+        assert schema is not None
+
+    def test_get_response_schema_not_found(self, temp_spec_file):
+        """Test response schema not found for undefined status code."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+
+        schema = parser.get_response_schema("/users", "get", "500")
+        assert schema is None
+
+    def test_version_extraction(self, temp_spec_file):
+        """Test OpenAPI version extraction."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+
+        assert parser.version == "3.0.0"
+
+    def test_get_servers(self, temp_spec_file):
+        """Test extracting servers from specification."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+
+        servers = parser.get_servers()
+        assert isinstance(servers, list)
+
+    def test_get_base_path(self, temp_spec_file):
+        """Test extracting base path from specification."""
+        parser = OpenAPIParser(str(temp_spec_file))
+        parser.load()
+
+        base_path = parser.get_base_path()
+        assert isinstance(base_path, str)
+
+
+class TestOpenAPIParserErrors:
+    """Tests for parser error handling."""
+
+    def test_invalid_yaml_format(self, tmp_path):
+        """Test handling of invalid YAML format."""
+        invalid_file = tmp_path / "invalid.yaml"
+        invalid_file.write_text("not: valid: yaml: content: [")
+
+        parser = OpenAPIParser(str(invalid_file))
+
+        with pytest.raises(InvalidOpenAPIFormat):
+            parser.load()
+
+    def test_missing_openapi_version(self, tmp_path):
+        """Test handling of missing OpenAPI version."""
+        invalid_file = tmp_path / "missing_version.yaml"
+        invalid_file.write_text("""
+info:
+  title: Test API
+  version: \"1.0.0\"
+paths: {}
+""")
+
+        parser = OpenAPIParser(str(invalid_file))
+
+        with pytest.raises(InvalidOpenAPIFormat):
+            parser.load()
+
+    def test_unsupported_version(self, tmp_path):
+        """Test handling of unsupported OpenAPI version."""
+        invalid_file = tmp_path / "unsupported.yaml"
+        invalid_file.write_text("""
+openapi: \"2.0.0\"
+info:
+  title: Test API
+  version: \"1.0.0\"
+paths: {}
+""")
+
+        parser = OpenAPIParser(str(invalid_file))
+
+        with pytest.raises(UnsupportedOpenAPIVersion):
+            parser.load()
+
+    def test_invalid_json_format(self, tmp_path):
+        """Test handling of invalid JSON format."""
+        invalid_file = tmp_path / "invalid.json"
+        invalid_file.write_text("{invalid json}")
+
+        parser = OpenAPIParser(str(invalid_file))
+
+        with pytest.raises(InvalidOpenAPIFormat):
+            parser.load()