bpo-40280: Skip socket, fork, subprocess tests on Emscripten (GH-31986)

- Add requires_fork and requires_subprocess to more tests
- Skip extension import tests if dlopen is not available
- Don't assume that _testcapi is a shared extension
- Skip a lot of socket tests that don't work on Emscripten
- Skip mmap tests, mmap emulation is incomplete
- venv does not work yet
- Cannot get libc from executable

The "entire" test suite is now passing on Emscripten with EMSDK from git head (91 suites are skipped).

5 files changed, 12 insertions, 1 deletions

diff --git a/Lib/unittest/test/__init__.py b/Lib/unittest/test/__init__.py
index cdae8a7..143f4ab 100644
--- a/Lib/unittest/test/__init__.py
+++ b/Lib/unittest/test/__init__.py
@@ -11,7 +11,10 @@ def suite():
     for fn in os.listdir(here):
         if fn.startswith("test") and fn.endswith(".py"):
             modname = "unittest.test." + fn[:-3]
-            __import__(modname)
+            try:
+                __import__(modname)
+            except unittest.SkipTest:
+                continue
             module = sys.modules[modname]
             suite.addTest(loader.loadTestsFromModule(module))
     suite.addTest(loader.loadTestsFromName('unittest.test.testmock'))
diff --git a/Lib/unittest/test/test_async_case.py b/Lib/unittest/test/test_async_case.py
index 7dc8a6b..a481408 100644
--- a/Lib/unittest/test/test_async_case.py
+++ b/Lib/unittest/test/test_async_case.py
@@ -3,6 +3,8 @@ import contextvars
 import unittest
 from test import support
 
+support.requires_working_socket(module=True)
+
 
 class MyException(Exception):
     pass
diff --git a/Lib/unittest/test/test_program.py b/Lib/unittest/test/test_program.py
index fa9e629..126497a 100644
--- a/Lib/unittest/test/test_program.py
+++ b/Lib/unittest/test/test_program.py
@@ -196,6 +196,7 @@ class FakeRunner(object):
         return RESULT
 
 
+@support.requires_subprocess()
 class TestCommandLineArgs(unittest.TestCase):
 
     def setUp(self):
diff --git a/Lib/unittest/test/test_runner.py b/Lib/unittest/test/test_runner.py
index c487e9e..18062ae 100644
--- a/Lib/unittest/test/test_runner.py
+++ b/Lib/unittest/test/test_runner.py
@@ -3,6 +3,7 @@ import os
 import sys
 import pickle
 import subprocess
+from test import support
 
 import unittest
 from unittest.case import _Outcome
@@ -1139,6 +1140,7 @@ class Test_TextTestRunner(unittest.TestCase):
         expectedresult = (runner.stream, DESCRIPTIONS, VERBOSITY)
         self.assertEqual(runner._makeResult(), expectedresult)
 
+    @support.requires_subprocess()
     def test_warnings(self):
         """
         Check that warnings argument of TextTestRunner correctly affects the
diff --git a/Lib/unittest/test/testmock/testasync.py b/Lib/unittest/test/testmock/testasync.py
index 122e695..1bab671 100644
--- a/Lib/unittest/test/testmock/testasync.py
+++ b/Lib/unittest/test/testmock/testasync.py
@@ -4,6 +4,9 @@ import inspect
 import re
 import unittest
 from contextlib import contextmanager
+from test import support
+
+support.requires_working_socket(module=True)
 
 from asyncio import run, iscoroutinefunction
 from unittest import IsolatedAsyncioTestCase