See if we can fix tests on win and mac.

src/twisted/conch/test/test_filetransfer.py

@@ -855,6 +855,9 @@ def test_constantsAgainstSpec(self):
             self.assertEqual(v, getattr(filetransfer, k))
 
 
+# We don't run on Windows, as we don't have an SFTP file server implemented in conch.ssh for Windows.
+# As soon as there is such an implementation, we can run these tests on Windows.
+@skipIf(not unix, "can't run on non-posix computers")
 @skipIf(not cryptography, "Cannot run without cryptography")
 class RawPacketDataServerTests(TestCase):
     """

src/twisted/internet/test/test_posixbase.py

@@ -297,4 +297,4 @@ def test_noWakerConstructionWarnings(self):
         warnings = self.flushWarnings()
         # explicitly close the sockets
         waker.connectionLost(None)
-        self.assertEqual(len(warnings), 0)
+        self.assertEqual(len(warnings), 0, warnings)

src/twisted/internet/test/test_process.py

@@ -428,7 +428,8 @@ def test_openFileDescriptors(self):
         # might at least hypothetically select.)
 
         fudgeFactor = 17
-        unlikelyFD = resource.getrlimit(resource.RLIMIT_NOFILE)[0] - fudgeFactor
+        # Try not to go into negative land.
+        unlikelyFD = max(9, resource.getrlimit(resource.RLIMIT_NOFILE)[0] - fudgeFactor)
 
         os.dup2(w, unlikelyFD)
         self.addCleanup(os.close, unlikelyFD)

src/twisted/trial/test/test_util.py

@@ -634,8 +634,8 @@ def test_append(self):
         The log file is opened in append mode so if runner configuration specifies
         an existing log file its contents are not wiped out.
         """
-        existingText = "Hello, world.\n"
-        newText = "Goodbye, world.\n"
+        existingText = f"Hello, world.{os.linesep} "
+        newText = f"Goodbye, world.{os.linesep}"
         p = filepath.FilePath(self.mktemp())
         with openTestLog(p) as f:
             f.write(existingText)