Allow setting `$TEST_RANDOMIZE_ORDERING_SEED` after absltest import.

The goal is allowing users to customize this env var programmatically *after*
all imports but *before* beginning test execution.

PiperOrigin-RevId: 287881783
Change-Id: I6c1a18ff541194d1a416025ceb7fc33e1d414cf1

3 files changed, 32 insertions, 10 deletions

diff --git a/absl/testing/absltest.py b/absl/testing/absltest.py
index 180f904..6362bef 100644
--- a/absl/testing/absltest.py
+++ b/absl/testing/absltest.py
@@ -207,7 +207,12 @@ def _get_default_randomize_ordering_seed():
     ValueError: Raised when the flag or env value is not one of the options
         above.
   """
-  randomize = FLAGS.test_randomize_ordering_seed
+  if FLAGS['test_randomize_ordering_seed'].present:
+    randomize = FLAGS.test_randomize_ordering_seed
+  elif 'TEST_RANDOMIZE_ORDERING_SEED' in os.environ:
+    randomize = os.environ['TEST_RANDOMIZE_ORDERING_SEED']
+  else:
+    randomize = ''
   if not randomize:
     return 0
   if randomize == 'random':
@@ -236,14 +241,15 @@ flags.DEFINE_string('test_srcdir',
 flags.DEFINE_string('test_tmpdir', get_default_test_tmpdir(),
                     'Directory for temporary testing files',
                     allow_override_cpp=True)
-flags.DEFINE_string('test_randomize_ordering_seed',
-                    os.environ.get('TEST_RANDOMIZE_ORDERING_SEED', ''),
-                    'If positive, use this as a seed to randomize the '
-                    'execution order for test cases. If "random", pick a '
-                    'random seed to use. If 0 or not set, do not randomize '
-                    'test case execution order. This flag also overrides '
-                    'the TEST_RANDOMIZE_ORDERING_SEED environment variable.',
-                    allow_override_cpp=True)
+flags.DEFINE_string(
+    'test_randomize_ordering_seed',
+    '',
+    'If positive, use this as a seed to randomize the '
+    'execution order for test cases. If "random", pick a '
+    'random seed to use. If 0 or not set, do not randomize '
+    'test case execution order. This flag also overrides '
+    'the TEST_RANDOMIZE_ORDERING_SEED environment variable.',
+    allow_override_cpp=True)
 flags.DEFINE_string('xml_output_file', '',
                     'File to store XML test results')
 
diff --git a/absl/testing/tests/absltest_randomization_test.py b/absl/testing/tests/absltest_randomization_test.py
index 62ea2c2..16b330c 100644
--- a/absl/testing/tests/absltest_randomization_test.py
+++ b/absl/testing/tests/absltest_randomization_test.py
@@ -37,6 +37,7 @@ class TestOrderRandomizationTest(parameterized.TestCase):
   """
 
   def setUp(self):
+    super(TestOrderRandomizationTest, self).setUp()
     self._test_name = 'absl/testing/tests/absltest_randomization_testcase'
 
   def _run_test(self, extra_argv, extra_env):
@@ -107,7 +108,14 @@ class TestOrderRandomizationTest(parameterized.TestCase):
           'env': {
               'TEST_RANDOMIZE_ORDERING_SEED': '1'
           },
-      },)
+      },
+      {
+          'argv': [],
+          'env': {
+              'LATE_SET_TEST_RANDOMIZE_ORDERING_SEED': '1'
+          },
+      },
+  )
   def test_fixed_seed(self, argv, env):
     output, tests, exit_code = self._run_test(argv, env)
     self.assertEqual(0, exit_code, msg='command output: ' + output)
diff --git a/absl/testing/tests/absltest_randomization_testcase.py b/absl/testing/tests/absltest_randomization_testcase.py
index 25ce228..18b20ff 100644
--- a/absl/testing/tests/absltest_randomization_testcase.py
+++ b/absl/testing/tests/absltest_randomization_testcase.py
@@ -18,11 +18,19 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
+import os
 import sys
 
 from absl.testing import absltest
 
 
+# This stanza exercises setting $TEST_RANDOMIZE_ORDERING_SEED *after* importing
+# the absltest library.
+if os.environ.get('LATE_SET_TEST_RANDOMIZE_ORDERING_SEED', ''):
+  os.environ['TEST_RANDOMIZE_ORDERING_SEED'] = os.environ[
+      'LATE_SET_TEST_RANDOMIZE_ORDERING_SEED']
+
+
 class ClassA(absltest.TestCase):
 
   def test_a(self):