diff --git a/tests/unit/test_parsers.py b/tests/unit/test_parsers.py
new file mode 100644
index 0000000..a0c93fc
--- /dev/null
+++ b/tests/unit/test_parsers.py
@@ -0,0 +1,248 @@
+"""Tests for package parsers."""
+
+import tempfile
+import os
+from pathlib import Path
+
+import pytest
+
+from depcheck.models import PackageManager
+from depcheck.parsers import create_parser_registry
+from depcheck.parsers.cargo import CargoParser
+from depcheck.parsers.go import GoParser
+from depcheck.parsers.npm import NpmParser
+from depcheck.parsers.pip import PipParser
+
+
+class TestNpmParser:
+    """Tests for NPM package.json parser."""
+
+    def test_parse_simple_package_json(self):
+        """Test parsing a simple package.json."""
+        content = """{
+            "name": "test-project",
+            "version": "1.0.0",
+            "dependencies": {
+                "express": "4.18.2",
+                "lodash": "4.17.21"
+            }
+        }"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pkg_path = Path(tmpdir) / "package.json"
+            pkg_path.write_text(content)
+
+            parser = NpmParser()
+            deps = parser.parse(pkg_path)
+
+        assert len(deps) == 2
+        assert any(d.name == "express" for d in deps)
+        assert any(d.name == "lodash" for d in deps)
+
+    def test_parse_dev_dependencies(self):
+        """Test parsing devDependencies."""
+        content = """{
+            "name": "test-project",
+            "devDependencies": {
+                "jest": "29.7.0",
+                "eslint": "8.56.0"
+            }
+        }"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pkg_path = Path(tmpdir) / "package.json"
+            pkg_path.write_text(content)
+
+            parser = NpmParser()
+            deps = parser.parse(pkg_path)
+
+        assert len(deps) == 2
+        assert all(d.category == "devDependencies" for d in deps)
+
+    def test_parse_optional_dependencies(self):
+        """Test parsing optionalDependencies."""
+        content = """{
+            "optionalDependencies": {
+                "fsevents": "2.3.3"
+            }
+        }"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pkg_path = Path(tmpdir) / "package.json"
+            pkg_path.write_text(content)
+
+            parser = NpmParser()
+            deps = parser.parse(pkg_path)
+
+        assert len(deps) == 1
+        assert deps[0].category == "optionalDependencies"
+
+    def test_invalid_json_handled_gracefully(self):
+        """Test that invalid JSON is handled gracefully."""
+        content = "{ invalid json }"
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pkg_path = Path(tmpdir) / "package.json"
+            pkg_path.write_text(content)
+
+            parser = NpmParser()
+            deps = parser.parse(pkg_path)
+
+        assert len(deps) == 0
+
+
+class TestPipParser:
+    """Tests for pip requirements.txt parser."""
+
+    def test_parse_requirements_txt(self):
+        """Test parsing requirements.txt."""
+        content = """# This is a comment
+requests>=2.31.0
+flask>=2.0.0
+numpy==1.24.0
+"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            req_path = Path(tmpdir) / "requirements.txt"
+            req_path.write_text(content)
+
+            parser = PipParser()
+            deps = parser.parse(req_path)
+
+        assert len(deps) == 3
+        assert any(d.name == "requests" for d in deps)
+        assert any(d.name == "flask" for d in deps)
+        assert any(d.name == "numpy" for d in deps)
+
+    def test_parse_requirements_with_comments(self):
+        """Test that comments are ignored."""
+        content = """requests==2.31.0  # inline comment
+flask>=2.0.0; python_version >= \"3.8\"
+"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            req_path = Path(tmpdir) / "requirements.txt"
+            req_path.write_text(content)
+
+            parser = PipParser()
+            deps = parser.parse(req_path)
+
+        assert len(deps) >= 1
+
+    def test_parse_pyproject_toml(self):
+        """Test parsing pyproject.toml."""
+        content = """
+[project]
+dependencies = [
+    \"requests>=2.31.0\",
+    \"flask>=2.0.0\"
+]
+"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_path = Path(tmpdir) / "pyproject.toml"
+            toml_path.write_text(content)
+
+            parser = PipParser()
+            deps = parser.parse(toml_path)
+
+        assert len(deps) == 2
+
+
+class TestGoParser:
+    """Tests for Go go.mod parser."""
+
+    def test_parse_go_mod(self):
+        """Test parsing go.mod file."""
+        content = """
+module github.com/example/project
+
+go 1.21
+
+require (
+    github.com/stretchr/testify v1.8.4
+    golang.org/x/crypto v0.17.0
+)
+"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            mod_path = Path(tmpdir) / "go.mod"
+            mod_path.write_text(content)
+
+            parser = GoParser()
+            deps = parser.parse(mod_path)
+
+        assert len(deps) == 2
+        assert any("testify" in d.name for d in deps)
+        assert any("crypto" in d.name for d in deps)
+
+
+class TestCargoParser:
+    """Tests for Rust Cargo.toml parser."""
+
+    def test_parse_cargo_toml(self):
+        """Test parsing Cargo.toml file."""
+        content = """
+[package]
+name = "my-project"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+serde = "1.0"
+tokio = "1.36"
+
+[dev-dependencies]
+proptest = "1.4"
+"""
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            cargo_path = Path(tmpdir) / "Cargo.toml"
+            cargo_path.write_text(content)
+
+            parser = CargoParser()
+            deps = parser.parse(cargo_path)
+
+        assert len(deps) == 3
+        assert any(d.name == "serde" for d in deps)
+        assert any(d.name == "tokio" for d in deps)
+        assert any(d.name == "proptest" for d in deps)
+
+
+class TestParserRegistry:
+    """Tests for parser registry."""
+
+    def test_get_parser_for_package_json(self):
+        """Test getting correct parser for package.json."""
+        registry = create_parser_registry()
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pkg_path = Path(tmpdir) / "package.json"
+            pkg_path.write_text('{"name": "test"}')
+
+            parser = registry.get_parser(pkg_path)
+            assert parser is not None
+            assert parser.package_manager == PackageManager.NPM
+
+    def test_get_parser_for_requirements(self):
+        """Test getting correct parser for requirements.txt."""
+        registry = create_parser_registry()
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            req_path = Path(tmpdir) / "requirements.txt"
+            req_path.write_text("requests==2.31.0")
+
+            parser = registry.get_parser(req_path)
+            assert parser is not None
+            assert parser.package_manager == PackageManager.PIP
+
+    def test_no_parser_for_unknown_file(self):
+        """Test that unknown file types return None."""
+        registry = create_parser_registry()
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            unknown_path = Path(tmpdir) / "unknown.ext"
+            unknown_path.write_text("some content")
+
+            parser = registry.get_parser(unknown_path)
+            assert parser is None