diff --git a/tests/test_fixes.py b/tests/test_fixes.py
new file mode 100644
index 0000000..d8c8f81
--- /dev/null
+++ b/tests/test_fixes.py
@@ -0,0 +1,139 @@
+import pytest
+from pathlib import Path
+import tempfile
+import os
+
+from config_auditor.fixes import (
+    Fixer,
+    DeprecatedPackageFixer,
+    AddTestScriptFixer,
+    EnableStrictModeFixer,
+)
+
+
+class TestDeprecatedPackageFixer:
+    def test_can_fix_deprecated(self):
+        fixer = DeprecatedPackageFixer()
+        data = {"dependencies": {"request": "^2.0.0"}}
+
+        assert fixer.can_fix(data, Path("package.json")) is True
+
+    def test_cannot_fix_when_no_deprecated(self):
+        fixer = DeprecatedPackageFixer()
+        data = {"dependencies": {"express": "^4.0.0"}}
+
+        assert fixer.can_fix(data, Path("package.json")) is False
+
+    def test_apply_fix(self):
+        fixer = DeprecatedPackageFixer()
+        data = {"dependencies": {"request": "^2.0.0"}}
+        result = fixer.apply_fix(data, Path("package.json"))
+
+        assert "requests" in result["dependencies"]
+        assert "request" not in result["dependencies"]
+
+
+class TestAddTestScriptFixer:
+    def test_can_fix_missing_test(self):
+        fixer = AddTestScriptFixer()
+        data = {"scripts": {}}
+
+        assert fixer.can_fix(data, Path("package.json")) is True
+
+    def test_cannot_fix_when_test_exists(self):
+        fixer = AddTestScriptFixer()
+        data = {"scripts": {"test": "jest"}}
+
+        assert fixer.can_fix(data, Path("package.json")) is False
+
+    def test_apply_fix(self):
+        fixer = AddTestScriptFixer()
+        data = {"scripts": {}}
+        result = fixer.apply_fix(data, Path("package.json"))
+
+        assert "test" in result["scripts"]
+        assert "build" in result["scripts"]
+
+
+class TestEnableStrictModeFixer:
+    def test_can_fix_missing_strict(self):
+        fixer = EnableStrictModeFixer()
+        data = {"compilerOptions": {}}
+
+        assert fixer.can_fix(data, Path("tsconfig.json")) is True
+
+    def test_cannot_fix_when_strict_enabled(self):
+        fixer = EnableStrictModeFixer()
+        data = {"compilerOptions": {"strict": True}}
+
+        assert fixer.can_fix(data, Path("tsconfig.json")) is False
+
+    def test_apply_fix(self):
+        fixer = EnableStrictModeFixer()
+        data = {"compilerOptions": {}}
+        result = fixer.apply_fix(data, Path("tsconfig.json"))
+
+        assert result["compilerOptions"]["strict"] is True
+
+
+class TestFixer:
+    def test_dry_run_does_not_modify_file(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "package.json"
+            content = '{"name": "test", "scripts": {}}'
+            config_path.write_text(content)
+
+            fixer = Fixer(dry_run=True)
+            fix_count = fixer.fix_config(config_path, "json", content)
+
+            actual_content = config_path.read_text()
+            assert actual_content == content
+
+    def test_force_applies_fixes_without_confirm(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "package.json"
+            content = '{"name": "test", "scripts": {}}'
+            config_path.write_text(content)
+
+            fixer = Fixer(force=True)
+            fix_count = fixer.fix_config(config_path, "json", content)
+
+            assert fix_count > 0
+            actual_content = config_path.read_text()
+            assert '"test"' in actual_content
+
+    def test_returns_fix_count(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "package.json"
+            content = '{"name": "test", "scripts": {}}'
+            config_path.write_text(content)
+
+            fixer = Fixer(force=True)
+            fix_count = fixer.fix_config(config_path, "json", content)
+
+            assert fix_count >= 1
+
+    def test_invalid_content_returns_zero(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "package.json"
+            config_path.write_text("not valid json")
+
+            fixer = Fixer(force=True)
+            fix_count = fixer.fix_config(config_path, "json", "not valid json")
+
+            assert fix_count == 0
+
+    def test_backup_created_on_fix(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "package.json"
+            content = '{"name": "test", "scripts": {}}'
+            config_path.write_text(content)
+
+            fixer = Fixer(force=True)
+            fixer.fix_config(config_path, "json", content)
+
+            backup_path = Path(".config_auditor_backup") / "package.json.bak"
+            if backup_path.exists():
+                backup_content = backup_path.read_text()
+                assert "name" in backup_content
+                assert "test" in backup_content