diff --git a/l2tdevtools/review_helpers/review.py b/l2tdevtools/review_helpers/review.py
index 4f6258de..ff829f5d 100644
--- a/l2tdevtools/review_helpers/review.py
+++ b/l2tdevtools/review_helpers/review.py
@@ -21,6 +21,16 @@ class ReviewHelper:
         ["create-pr", "create_pr", "lint", "lint-test", "lint_test"]
     )
 
+    _FULL_TEST_FILES = frozenset(
+        [
+            "dependencies.ini",
+            "pyproject.toml",
+            "run_tests.py",
+            "test_dependencies.ini",
+            "tox.ini",
+        ]
+    )
+
     def __init__(
         self, command, project_path, github_origin, feature_branch, all_files=False
     ):
@@ -31,8 +41,8 @@ def __init__(
           project_path (str): path to the project being reviewed.
           github_origin (str): GitHub origin.
           feature_branch (str): feature branch.
-          all_files (Optional[bool]): True if the command should apply to all
-              files. Currently this only affects the lint command.
+          all_files (Optional[bool]): True if lint and test commands should
+              apply to all files.
         """
         super().__init__()
         self._active_branch = None
@@ -178,6 +188,44 @@ def InitializeHelpers(self):
 
         return True
 
+    def _GetChangedTestModules(self):
+        """Determines test modules corresponding to changed Python files.
+
+        Returns:
+          list[str]: test module names, an empty list if no Python files were
+              changed, or None if the complete test suite should be run.
+        """
+        changed_files = self._git_helper.GetChangedFiles(diffbase="main")
+        if any(changed_file in self._FULL_TEST_FILES for changed_file in changed_files):
+            return None
+
+        test_files = set()
+        project_source_prefix = f"{self._project_name:s}/"
+        for changed_file in changed_files:
+            if not changed_file.endswith(".py"):
+                continue
+
+            if os.path.basename(changed_file) in ("__init__.py", "interface.py"):
+                return None
+
+            if changed_file.startswith("tests/"):
+                test_file = changed_file
+            elif changed_file.startswith(project_source_prefix):
+                test_file = changed_file.replace(project_source_prefix, "tests/", 1)
+            else:
+                return None
+
+            test_path = os.path.join(self._project_path, test_file)
+            if not os.path.exists(test_path):
+                return None
+
+            test_files.add(test_file)
+
+        return [
+            os.path.splitext(test_file)[0].replace("/", ".").replace("\\", ".")
+            for test_file in sorted(test_files)
+        ]
+
     def Lint(self):
         """Lints a review.
 
@@ -234,10 +282,18 @@ def Test(self):
         ):
             return True
 
-        # TODO: determine why this alters the behavior of argparse.
-        # Currently affects this script being used in plaso.
-        command = f"{sys.executable:s} run_tests.py"
-        exit_code = subprocess.call(command, shell=True)
+        test_modules = None
+        if not self._all_files:
+            test_modules = self._GetChangedTestModules()
+            if test_modules == []:
+                return True
+
+        if test_modules is None:
+            command = [sys.executable, "run_tests.py"]
+        else:
+            command = [sys.executable, "-m", "unittest", *test_modules]
+
+        exit_code = subprocess.call(command)
         if exit_code != 0:
             command_title = self._command.title()
             print(f"{command_title:s} aborted - unable to pass review.")
diff --git a/tests/review_helpers/review.py b/tests/review_helpers/review.py
index ae3c5f85..779b522f 100644
--- a/tests/review_helpers/review.py
+++ b/tests/review_helpers/review.py
@@ -1,7 +1,10 @@
 #!/usr/bin/env python3
 """Tests for the review helper."""
 
+import os
+import sys
 import unittest
+from unittest import mock
 
 from l2tdevtools.review_helpers import review
 
@@ -22,6 +25,50 @@ def testInitialize(self):
         )
         self.assertIsNotNone(helper)
 
+    @mock.patch("l2tdevtools.review_helpers.review.subprocess.call")
+    def testTestChangedFiles(self, mock_subprocess_call):
+        """Tests running tests selected from changed files."""
+        mock_subprocess_call.return_value = 0
+
+        project_path = os.path.dirname(
+            os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+        )
+        helper = review.ReviewHelper("test", project_path, None, None)
+        helper._project_name = "l2tdevtools"
+        helper._git_helper = mock.Mock()
+
+        helper._git_helper.GetChangedFiles.return_value = [
+            "l2tdevtools/review_helpers/review.py"
+        ]
+        self.assertTrue(helper.Test())
+        mock_subprocess_call.assert_called_once_with(
+            [sys.executable, "-m", "unittest", "tests.review_helpers.review"]
+        )
+
+        helper._project_name = "dfvfs"
+        helper._git_helper.GetChangedFiles.return_value = [
+            "dfvfs/review_helpers/review.py"
+        ]
+        mock_subprocess_call.reset_mock()
+        self.assertTrue(helper.Test())
+        mock_subprocess_call.assert_called_once_with(
+            [sys.executable, "-m", "unittest", "tests.review_helpers.review"]
+        )
+
+        helper._git_helper.GetChangedFiles.return_value = ["README.md"]
+        mock_subprocess_call.reset_mock()
+        self.assertTrue(helper.Test())
+        mock_subprocess_call.assert_not_called()
+
+        helper._git_helper.GetChangedFiles.return_value = ["pyproject.toml"]
+        self.assertTrue(helper.Test())
+        mock_subprocess_call.assert_called_once_with([sys.executable, "run_tests.py"])
+
+        helper._all_files = True
+        mock_subprocess_call.reset_mock()
+        self.assertTrue(helper.Test())
+        mock_subprocess_call.assert_called_once_with([sys.executable, "run_tests.py"])
+
     # TODO: test CheckLocalGitState.
     # TODO: test CheckRemoteGitState.
     # TODO: test Close.
diff --git a/tools/review.py b/tools/review.py
old mode 100755
new mode 100644
index 86a35e37..42893707
--- a/tools/review.py
+++ b/tools/review.py
@@ -33,9 +33,7 @@ def Main():
         dest="all_files",
         action="store_true",
         default=False,
-        help=(
-            "Apply command to all files, currently only affects the lint " "command."
-        ),
+        help="Apply the lint or test command to all files.",
     )
     commands_parser = argument_parser.add_subparsers(dest="command")