diff --git a/codebasin/preprocessor.py b/codebasin/preprocessor.py
index 1b1d342..ce45311 100644
--- a/codebasin/preprocessor.py
+++ b/codebasin/preprocessor.py
@@ -11,7 +11,9 @@
 import hashlib
 import logging
 import os
+from collections.abc import Iterable
 from copy import copy
+from typing import Self
 
 import numpy as np
 
@@ -583,6 +585,18 @@ def evaluate_for_platform(self, **kwargs):
         """
         return False
 
+    def walk(self) -> Iterable[Self]:
+        """
+        Returns
+        -------
+        Iterable[Self]
+            An Iterable visiting all descendants of this node via a preorder
+            traversal.
+        """
+        yield self
+        for child in self.children:
+            yield from child.walk()
+
 
 class FileNode(Node):
     """
@@ -2330,6 +2344,16 @@ def __init__(self, filename):
         self.root = FileNode(filename)
         self._latest_node = self.root
 
+    def walk(self) -> Iterable[Node]:
+        """
+        Returns
+        -------
+        Iterable[Node]
+            An Iterable visiting all nodes in the tree via a preorder
+            traversal.
+        """
+        yield from self.root.walk()
+
     def associate_file(self, filename):
         self.root.filename = filename
 
diff --git a/tests/source-tree/__init__.py b/tests/source-tree/__init__.py
new file mode 100644
index 0000000..94adb81
--- /dev/null
+++ b/tests/source-tree/__init__.py
@@ -0,0 +1,2 @@
+# Copyright (C) 2019-2024 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause
diff --git a/tests/source-tree/test_source_tree.py b/tests/source-tree/test_source_tree.py
new file mode 100644
index 0000000..4d9463a
--- /dev/null
+++ b/tests/source-tree/test_source_tree.py
@@ -0,0 +1,79 @@
+# Copyright (C) 2019-2024 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause
+
+import logging
+import tempfile
+import unittest
+import warnings
+
+from codebasin.file_parser import FileParser
+from codebasin.preprocessor import CodeNode, DirectiveNode, FileNode
+
+
+class TestSourceTree(unittest.TestCase):
+    """
+    Test SourceTree class.
+    """
+
+    def setUp(self):
+        logging.getLogger("codebasin").disabled = False
+        warnings.simplefilter("ignore", ResourceWarning)
+
+    def test_walk(self):
+        """Check that walk() visits nodes in the expected order"""
+
+        # TODO: Revisit this when SourceTree can be built without a file.
+        with tempfile.NamedTemporaryFile(
+            mode="w",
+            delete_on_close=False,
+            suffix=".cpp",
+        ) as f:
+            source = """
+                #if defined(FOO)
+                void foo();
+                #elif defined(BAR)
+                void bar();
+                #else
+                void baz();
+                #endif
+
+                void qux();
+                """
+            f.write(source)
+            f.close()
+
+            # TODO: Revisit this when __str__() is more reliable.
+            tree = FileParser(f.name).parse_file(summarize_only=False)
+            expected_types = [
+                FileNode,
+                DirectiveNode,
+                CodeNode,
+                DirectiveNode,
+                CodeNode,
+                DirectiveNode,
+                CodeNode,
+                DirectiveNode,
+                CodeNode,
+            ]
+            expected_contents = [
+                f.name,
+                "FOO",
+                "foo",
+                "BAR",
+                "bar",
+                "else",
+                "baz",
+                "endif",
+                "qux",
+            ]
+            for i, node in enumerate(tree.walk()):
+                self.assertTrue(isinstance(node, expected_types[i]))
+                if isinstance(node, CodeNode):
+                    contents = node.spelling()[0]
+                else:
+                    contents = str(node)
+                self.assertTrue(expected_contents[i] in contents)
+
+
+if __name__ == "__main__":
+    unittest.main()