diff --git a/debuginfo-tests/dexter/d.diff b/debuginfo-tests/dexter/d.diff
deleted file mode 100644
index fef582c146258..0000000000000
--- a/debuginfo-tests/dexter/d.diff
+++ /dev/null
@@ -1,463 +0,0 @@
-diff --git a/debuginfo-tests/dexter/Commands.md b/debuginfo-tests/dexter/Commands.md
-index 5de685906c01..da14b8d59ba7 100644
---- a/debuginfo-tests/dexter/Commands.md
-+++ b/debuginfo-tests/dexter/Commands.md
-@@ -9,6 +9,7 @@
- * [DexLimitSteps](Commands.md#DexLimitSteps)
- * [DexLabel](Commands.md#DexLabel)
- * [DexWatch](Commands.md#DexWatch)
-+* [DexDeclareFile](Commands.md#DexDeclareFile)
- 
- ---
- ## DexExpectProgramState
-@@ -231,6 +232,23 @@ arithmetic operators to get offsets from labels:
- ### Heuristic
- This command does not contribute to the heuristic score.
- 
-+----
-+## DexDeclareFile
-+    DexDeclareFile(declared_file)
-+
-+    Args:
-+        name (str): A declared file path for which all subsequent commands
-+          will have their path attribute set too.
-+
-+### Description
-+Set the path attribute of all commands from this point in the test onwards.
-+The new path holds until the end of the test file or until a new DexDeclareFile
-+command is encountered. Used in conjunction with .dex files, DexDeclareFile can
-+be used to write your dexter commands in a separate test file avoiding inlined
-+Dexter commands mixed with test source.
-+
-+### Heuristic
-+This command does not contribute to the heuristic score.
- 
- ---
- ## DexWatch
-diff --git a/debuginfo-tests/dexter/dex/command/ParseCommand.py b/debuginfo-tests/dexter/dex/command/ParseCommand.py
-index c9908ef4b399..81e5c6c117f0 100644
---- a/debuginfo-tests/dexter/dex/command/ParseCommand.py
-+++ b/debuginfo-tests/dexter/dex/command/ParseCommand.py
-@@ -12,12 +12,13 @@ Python code being embedded within DExTer commands.
- import os
- import unittest
- from copy import copy
--
-+from pathlib import PurePath
- from collections import defaultdict, OrderedDict
- 
- from dex.utils.Exceptions import CommandParseError
- 
- from dex.command.CommandBase import CommandBase
-+from dex.command.commands.DexDeclareFile import DexDeclareFile
- from dex.command.commands.DexExpectProgramState import DexExpectProgramState
- from dex.command.commands.DexExpectStepKind import DexExpectStepKind
- from dex.command.commands.DexExpectStepOrder import DexExpectStepOrder
-@@ -37,6 +38,7 @@ def _get_valid_commands():
-         { name (str): command (class) }
-     """
-     return {
-+      DexDeclareFile.get_name() : DexDeclareFile,
-       DexExpectProgramState.get_name() : DexExpectProgramState,
-       DexExpectStepKind.get_name() : DexExpectStepKind,
-       DexExpectStepOrder.get_name() : DexExpectStepOrder,
-@@ -209,6 +211,8 @@ def add_line_label(labels, label, cmd_path, cmd_lineno):
- 
- def _find_all_commands_in_file(path, file_lines, valid_commands):
-     labels = {} # dict of {name: line}.
-+    cmd_path = path
-+    declared_files = set()
-     commands = defaultdict(dict)
-     paren_balance = 0
-     region_start = TextPoint(0, 0)
-@@ -253,7 +257,7 @@ def _find_all_commands_in_file(path, file_lines, valid_commands):
-                     valid_commands[command_name],
-                     labels,
-                     raw_text,
--                    path,
-+                    cmd_path,
-                     cmd_point.get_lineno(),
-                 )
-             except SyntaxError as e:
-@@ -271,6 +275,14 @@ def _find_all_commands_in_file(path, file_lines, valid_commands):
-             else:
-                 if type(command) is DexLabel:
-                     add_line_label(labels, command, path, cmd_point.get_lineno())
-+                elif type(command) is DexDeclareFile:
-+                    cmd_path = command.declared_file
-+                    if not os.path.isabs(cmd_path):
-+                        source_dir = os.path.dirname(path)
-+                        cmd_path = os.path.join(source_dir, cmd_path)
-+                    # TODO: keep stored paths as PurePaths for 'longer'.
-+                    cmd_path = str(PurePath(cmd_path))
-+                    declared_files.add(cmd_path)
-                 assert (path, cmd_point) not in commands[command_name], (
-                     command_name, commands[command_name])
-                 commands[command_name][path, cmd_point] = command
-@@ -281,32 +293,34 @@ def _find_all_commands_in_file(path, file_lines, valid_commands):
-         err_point.char += len(command_name)
-         msg = "Unbalanced parenthesis starting here"
-         raise format_parse_err(msg, path, file_lines, err_point)
--    return dict(commands)
-+    return dict(commands), declared_files
- 
--def _find_all_commands(source_files):
-+def _find_all_commands(test_files):
-     commands = defaultdict(dict)
-     valid_commands = _get_valid_commands()
--    for source_file in source_files:
--        with open(source_file) as fp:
-+    new_source_files = set()
-+    for test_file in test_files:
-+        with open(test_file) as fp:
-             lines = fp.readlines()
--        file_commands = _find_all_commands_in_file(source_file, lines,
--                                                   valid_commands)
-+        file_commands, declared_files = _find_all_commands_in_file(test_file,
-+                                                  lines, valid_commands)
-         for command_name in file_commands:
-             commands[command_name].update(file_commands[command_name])
-+        new_source_files |= declared_files
- 
--    return dict(commands)
-+    return dict(commands), new_source_files
- 
--def get_command_infos(source_files):
-+def get_command_infos(test_files):
-   with Timer('parsing commands'):
-       try:
--          commands = _find_all_commands(source_files)
-+          commands, new_source_files = _find_all_commands(test_files)
-           command_infos = OrderedDict()
-           for command_type in commands:
-               for command in commands[command_type].values():
-                   if command_type not in command_infos:
-                       command_infos[command_type] = []
-                   command_infos[command_type].append(command)
--          return OrderedDict(command_infos)
-+          return OrderedDict(command_infos), new_source_files
-       except CommandParseError as e:
-           msg = 'parser error: <d>{}({}):</> {}\n{}\n{}\n'.format(
-                 e.filename, e.lineno, e.info, e.src, e.caret)
-@@ -344,7 +358,8 @@ class TestParseCommand(unittest.TestCase):
-         Returns:
-             { cmd_name: { (path, line): command_obj } }
-         """
--        return _find_all_commands_in_file(__file__, lines, self.valid_commands)
-+        cmds, declared_files = _find_all_commands_in_file(__file__, lines, self.valid_commands)
-+        return cmds
- 
- 
-     def _find_all_mock_values_in_lines(self, lines):
-diff --git a/debuginfo-tests/dexter/dex/command/commands/DexDeclareFile.py b/debuginfo-tests/dexter/dex/command/commands/DexDeclareFile.py
-new file mode 100644
-index 000000000000..c40c854575d9
---- /dev/null
-+++ b/debuginfo-tests/dexter/dex/command/commands/DexDeclareFile.py
-@@ -0,0 +1,31 @@
-+# DExTer : Debugging Experience Tester
-+# ~~~~~~   ~         ~~         ~   ~~
-+#
-+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-+# See https://llvm.org/LICENSE.txt for license information.
-+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-+"""Commmand sets the path for all following commands to 'declared_file'.
-+"""
-+
-+from pathlib import PurePath
-+
-+from dex.command.CommandBase import CommandBase
-+
-+
-+class DexDeclareFile(CommandBase):
-+    def __init__(self, declared_file):
-+
-+        if not isinstance(declared_file, str):
-+            raise TypeError('invalid argument type')
-+
-+        # Use PurePath to create a cannonical platform path.
-+        # TODO: keep paths as PurePath objects for 'longer'
-+        self.declared_file = str(PurePath(declared_file))
-+        super(DexDeclareFile, self).__init__()
-+
-+    @staticmethod
-+    def get_name():
-+        return __class__.__name__
-+
-+    def eval(self):
-+        return self.declared_file
-diff --git a/debuginfo-tests/dexter/dex/tools/TestToolBase.py b/debuginfo-tests/dexter/dex/tools/TestToolBase.py
-index a2d8a90c005e..cfea497124b5 100644
---- a/debuginfo-tests/dexter/dex/tools/TestToolBase.py
-+++ b/debuginfo-tests/dexter/dex/tools/TestToolBase.py
-@@ -100,26 +100,38 @@ class TestToolBase(ToolBase):
-         options.executable = os.path.join(
-             self.context.working_directory.path, 'tmp.exe')
- 
-+        # Test files contain dexter commands.
-+        options.test_files = []
-+        # Source files are to be compiled by the builder script and may also
-+        # contains dexter commands.
-+        options.source_files = []
-         if os.path.isdir(options.test_path):
--
-             subdirs = sorted([
-                 r for r, _, f in os.walk(options.test_path)
-                 if 'test.cfg' in f
-             ])
- 
-             for subdir in subdirs:
--
--                # TODO: read file extensions from the test.cfg file instead so
--                # that this isn't just limited to C and C++.
--                options.source_files = [
--                    os.path.normcase(os.path.join(subdir, f))
--                    for f in os.listdir(subdir) if any(
--                        f.endswith(ext) for ext in ['.c', '.cpp'])
--                ]
-+                for f in os.listdir(subdir):
-+                    # TODO: read file extensions from the test.cfg file instead so
-+                    # that this isn't just limited to C and C++.
-+                    file_path = os.path.normcase(os.path.join(subdir, f))
-+                    if f.endswith('.cpp'):
-+                        options.source_files.append(file_path)
-+                    elif f.endswith('.c'):
-+                        options.source_files.append(file_path)
-+                    elif f.endswith('.dex'):
-+                        options.test_files.append(file_path)
-+                # Source files can contain dexter commands too.
-+                options.test_files = options.test_files + options.source_files
- 
-                 self._run_test(self._get_test_name(subdir))
-         else:
--            options.source_files = [options.test_path]
-+            # We're dealing with a direct file path to a test file. If the file is non
-+            # .dex, then it must be a source file.
-+            if not options.test_path.endswith('.dex'):
-+                options.source_files = [options.test_path]
-+            options.test_files = [options.test_path]
-             self._run_test(self._get_test_name(options.test_path))
- 
-         return self._handle_results()
-diff --git a/debuginfo-tests/dexter/dex/tools/clang_opt_bisect/Tool.py b/debuginfo-tests/dexter/dex/tools/clang_opt_bisect/Tool.py
-index 6e936bd98a3c..c910d9c537ca 100644
---- a/debuginfo-tests/dexter/dex/tools/clang_opt_bisect/Tool.py
-+++ b/debuginfo-tests/dexter/dex/tools/clang_opt_bisect/Tool.py
-@@ -92,8 +92,9 @@ class Tool(TestToolBase):
-             executable_path=self.context.options.executable,
-             source_paths=self.context.options.source_files,
-             dexter_version=self.context.version)
--        step_collection.commands = get_command_infos(
--            self.context.options.source_files)
-+        step_collection.commands, new_source_files = get_command_infos(
-+            self.context.options.test_files)
-+        self.context.options.source_files.extend(list(new_source_files))
-         debugger_controller = DefaultController(self.context, step_collection)
-         return debugger_controller
- 
-diff --git a/debuginfo-tests/dexter/dex/tools/test/Tool.py b/debuginfo-tests/dexter/dex/tools/test/Tool.py
-index 43191fd44bd5..2d3ddce8f7b6 100644
---- a/debuginfo-tests/dexter/dex/tools/test/Tool.py
-+++ b/debuginfo-tests/dexter/dex/tools/test/Tool.py
-@@ -138,8 +138,10 @@ class Tool(TestToolBase):
-             source_paths=self.context.options.source_files,
-             dexter_version=self.context.version)
- 
--        step_collection.commands = get_command_infos(
--            self.context.options.source_files)
-+        step_collection.commands, new_source_files = get_command_infos(
-+            self.context.options.test_files)
-+
-+        self.context.options.source_files.extend(list(new_source_files))
- 
-         if 'DexLimitSteps' in step_collection.commands:
-             debugger_controller = ConditionalController(self.context, step_collection)
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/penalty/dex_declare_file.cpp b/debuginfo-tests/dexter/feature_tests/commands/penalty/dex_declare_file.cpp
-new file mode 100644
-index 000000000000..7860ffd5dda4
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/penalty/dex_declare_file.cpp
-@@ -0,0 +1,17 @@
-+// Purpose:
-+//    Check that \DexDeclareFile causes a DexExpectWatchValue's to generate a
-+//    missing value penalty when the declared path is incorrect.
-+//
-+// UNSUPPORTED: system-darwin
-+//
-+//
-+// RUN: not %dexter_regression_test -- %s | FileCheck %s
-+// CHECK: dex_declare_file.cpp
-+
-+int main() {
-+  int result = 0;
-+  return result; //DexLabel('return')
-+}
-+
-+// DexDeclareFile('this_file_does_not_exist.cpp')
-+// DexExpectWatchValue('result', 0, on_line='return')
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/commands.dex b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/commands.dex
-new file mode 100644
-index 000000000000..bbad7db943bf
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/commands.dex
-@@ -0,0 +1,2 @@
-+DexDeclareFile('test.cpp')
-+DexExpectWatchValue('result', 0, on_line=14)
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/lit.local.cfg.py b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/lit.local.cfg.py
-new file mode 100644
-index 000000000000..159c376beedb
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/lit.local.cfg.py
-@@ -0,0 +1 @@
-+config.suffixes = ['.cpp']
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/test.cfg b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/test.cfg
-new file mode 100644
-index 000000000000..e69de29bb2d1
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/test.cpp b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/test.cpp
-new file mode 100644
-index 000000000000..5f1d50efe8d0
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/dex_and_source/test.cpp
-@@ -0,0 +1,15 @@
-+// Purpose:
-+//    Check that \DexDeclareFile changes the path of all succeeding commands
-+//    to the file path it declares. Also check that dexter correctly accepts
-+//    files with .dex extensions.
-+//
-+// UNSUPPORTED: system-darwin
-+//
-+//
-+// RUN: %dexter_regression_test -- %S | FileCheck %s
-+// CHECK: dex_and_source
-+
-+int main() {
-+  int result = 0;
-+  return result;
-+}
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/commands.dex b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/commands.dex
-new file mode 100644
-index 000000000000..1aec2f8f3b64
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/commands.dex
-@@ -0,0 +1,18 @@
-+# Purpose:
-+#    Check that \DexDeclareFile's file declaration can reference source files
-+#    in a precompiled binary.
-+#
-+# UNSUPPORTED: system-darwin
-+#
-+# RUN: %clang %S/test.cpp -O0 -g -o %t
-+# RUN: %dexter_regression_test --binary %t %s | FileCheck %s
-+# CHECK: commands.dex
-+#
-+# test.cpp
-+# 1. int main() {
-+# 2.   int result = 0;
-+# 3.   return result;
-+# 4. }
-+
-+DexDeclareFile('test.cpp')
-+DexExpectWatchValue('result', 0, on_line=3)
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/lit.local.cfg.py b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/lit.local.cfg.py
-new file mode 100644
-index 000000000000..e65498f23dde
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/lit.local.cfg.py
-@@ -0,0 +1 @@
-+config.suffixes = ['.dex']
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/test.cpp b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/test.cpp
-new file mode 100644
-index 000000000000..4d3cc5846e66
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary/test.cpp
-@@ -0,0 +1,4 @@
-+int main() {
-+  int result = 0;
-+  return result;
-+}
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/dex_commands/commands.dex b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/dex_commands/commands.dex
-new file mode 100644
-index 000000000000..964c770d3325
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/dex_commands/commands.dex
-@@ -0,0 +1,19 @@
-+# Purpose:
-+#    Check that \DexDeclareFile's file declaration can reference source files
-+#    not included in the test directory
-+#
-+# UNSUPPORTED: system-darwin
-+#
-+# RUN: %clang %S/../source/test.cpp -O0 -g -o %t
-+# RUN: %dexter_regression_test --binary %t %s | FileCheck %s
-+# RUN: rm %t
-+# CHECK: commands.dex
-+#
-+# test.cpp
-+# 1. int main() {
-+# 2.   int result = 0;
-+# 3.   return result;
-+# 4. }
-+
-+DexDeclareFile('../source/test.cpp')
-+DexExpectWatchValue('result', 0, on_line=3)
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/lit.local.cfg.py b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/lit.local.cfg.py
-new file mode 100644
-index 000000000000..e65498f23dde
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/lit.local.cfg.py
-@@ -0,0 +1 @@
-+config.suffixes = ['.dex']
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/source/test.cpp b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/source/test.cpp
-new file mode 100644
-index 000000000000..4d3cc5846e66
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/precompiled_binary_different_dir/source/test.cpp
-@@ -0,0 +1,4 @@
-+int main() {
-+  int result = 0;
-+  return result;
-+}
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/lit.local.cfg.py b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/lit.local.cfg.py
-new file mode 100644
-index 000000000000..e65498f23dde
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/lit.local.cfg.py
-@@ -0,0 +1 @@
-+config.suffixes = ['.dex']
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/source/test file.cpp b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/source/test file.cpp
-new file mode 100644
-index 000000000000..f6dcd82e93e7
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/source/test file.cpp	
-@@ -0,0 +1,4 @@
-+int main(const int argc, const char * argv[]) {
-+  int result = argc;
-+  return result;
-+}
-\ No newline at end of file
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/test.cfg b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/test.cfg
-new file mode 100644
-index 000000000000..e69de29bb2d1
-diff --git a/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/test.dex b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/test.dex
-new file mode 100644
-index 000000000000..d9c9b80044b6
---- /dev/null
-+++ b/debuginfo-tests/dexter/feature_tests/commands/perfect/dex_declare_file/windows_noncanonical_path/test.dex
-@@ -0,0 +1,17 @@
-+# Purpose:
-+#    Check that non-canonical paths resolve correctly on Windows.
-+#
-+# REQUIRES: system-windows
-+#
-+# RUN: %clang "%S/source/test file.cpp" -O0 -g -o %t
-+# RUN: %dexter_regression_test --binary %t %s | FileCheck %s
-+# CHECK: test.dex
-+#
-+# ./source/test file.cpp
-+# 1 int main(const int argc, const char * argv[]) {
-+# 2 int result = argc;
-+# 3 return result;
-+# 4 }
-+
-+DexDeclareFile('./sOuRce\\test filE.cpp')
-+DexExpectWatchValue('result', 1, on_line=3)