diff --git a/tests/_data/empty.txt b/tests/_data/empty.txt
new file mode 100644
index 0000000..e69de29
diff --git a/tests/_data/imports.txt b/tests/_data/imports.txt
new file mode 100644
index 0000000..32eea8a
--- /dev/null
+++ b/tests/_data/imports.txt
@@ -0,0 +1,3 @@
+pandas==2.0.0
+numpy>=1.2.3
+torch<4.0.0
\ No newline at end of file
diff --git a/tests/test_pipreqs.py b/tests/test_pipreqs.py
index 039d4fd..6d90b6e 100644
--- a/tests/test_pipreqs.py
+++ b/tests/test_pipreqs.py
@@ -39,6 +39,13 @@ class TestPipreqs(unittest.TestCase):
         self.project = os.path.join(os.path.dirname(__file__), "_data")
         self.project_clean = os.path.join(os.path.dirname(__file__), "_data_clean")
         self.project_invalid = os.path.join(os.path.dirname(__file__), "_invalid_data")
+        self.parsed_packages = [
+            {"name": "pandas", "version": "2.0.0"},
+            {"name": "numpy", "version": "1.2.3"},
+            {"name": "torch", "version": "4.0.0"},
+        ]
+        self.empty_filepath = os.path.join(self.project, "empty.txt")
+        self.imports_filepath = os.path.join(self.project, "imports.txt")
         self.project_with_ignore_directory = os.path.join(
             os.path.dirname(__file__), "_data_ignore"
         )
@@ -427,6 +434,31 @@ class TestPipreqs(unittest.TestCase):
             data = f.read().lower()
             self.assertTrue(cleaned_module not in data)
 
+    def test_compare_modules(self):
+        test_cases = [
+            (self.empty_filepath, [], set()),  # both empty
+            (self.empty_filepath, self.parsed_packages, set()),  # only file empty
+            (
+                self.imports_filepath,
+                [],
+                set(package["name"] for package in self.parsed_packages),
+            ),  # only imports empty
+            (self.imports_filepath, self.parsed_packages, set()),  # no difference
+            (
+                self.imports_filepath,
+                self.parsed_packages[1:],
+                set([self.parsed_packages[0]["name"]]),
+            ),  # common case
+        ]
+
+        for test_case in test_cases:
+            with self.subTest(test_case):
+                filename, imports, expected_modules_not_imported = test_case
+
+                modules_not_imported = pipreqs.compare_modules(filename, imports)
+
+                self.assertSetEqual(modules_not_imported, expected_modules_not_imported)
+
     def tearDown(self):
         """
         Remove requiremnts.txt files that were written