diff --git a/rules/diff_test.bzl b/rules/diff_test.bzl
index 6fb3581..4482e6c 100644
--- a/rules/diff_test.bzl
+++ b/rules/diff_test.bzl
@@ -86,6 +86,9 @@ if [[ -d "${{RUNFILES_DIR:-/dev/null}}" && "${{RUNFILES_MANIFEST_ONLY:-}}" != 1
 elif [[ -f "${{RUNFILES_MANIFEST_FILE:-/dev/null}}" ]]; then
   RF1="$(grep -F -m1 "$F1 " "$RUNFILES_MANIFEST_FILE" | sed 's/^[^ ]* //')"
   RF2="$(grep -F -m1 "$F2 " "$RUNFILES_MANIFEST_FILE" | sed 's/^[^ ]* //')"
+elif [[ -f "$TEST_SRCDIR/$F1" && -f "$TEST_SRCDIR/$F2" ]]; then
+  RF1="$TEST_SRCDIR/$F1"
+  RF2="$TEST_SRCDIR/$F2"
 else
   echo >&2 "ERROR: could not find \"{file1}\" and \"{file2}\""
   exit 1
diff --git a/tests/diff_test/BUILD b/tests/diff_test/BUILD
index bd0aacd..aa381d8 100644
--- a/tests/diff_test/BUILD
+++ b/tests/diff_test/BUILD
@@ -13,6 +13,8 @@ sh_test(
         "//rules:diff_test",
         "//tests:unittest.bash",
     ],
+    # Test marked local because it uses bazel.
+    tags = ["local"],
     deps = ["@bazel_tools//tools/bash/runfiles"],
 )
 
diff --git a/tests/diff_test/diff_test_tests.sh b/tests/diff_test/diff_test_tests.sh
index aa43307..1cab39b 100755
--- a/tests/diff_test/diff_test_tests.sh
+++ b/tests/diff_test/diff_test_tests.sh
@@ -202,4 +202,5 @@ function test_from_ext_repo_without_legacy_external_runfiles() {
   assert_from_ext_repo "--nolegacy_external_runfiles" "${FUNCNAME[0]}"
 }
 
+cd "$TEST_TMPDIR"
 run_suite "diff_test_tests test suite"
diff --git a/tests/unittest_tests.bzl b/tests/unittest_tests.bzl
index 01ea4de..e25e4da 100644
--- a/tests/unittest_tests.bzl
+++ b/tests/unittest_tests.bzl
@@ -1,3 +1,17 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 """Unit tests for unittest.bzl."""
 
 load("//lib:unittest.bzl", "analysistest", "asserts", "unittest")