test: extend clipboard tests to various different sizes

Check if copying 64k also works. And then try copying 200kb, both
with default settings (should be refused) and with limit raised. This
test assume already modified behavior on over the limit copy (truncate
to 0 instead of truncating to the limit).
Finally, test copying 300k, which should be rejected regardless of the
limit.

Change also `zenity --entry` to `zenify --text-info --editable` as the
former supports only up to 65535 characters.

QubesOS/qubes-issues#9296

qubes/tests/integ/basic.py

@@ -472,7 +472,10 @@ def setUp(self):
         super(TC_30_Gui_daemon, self).setUp()
         self.init_default_template()
 
-    async def _test_clipboard(self, test_string):
+    async def _test_clipboard(self, test_string,
+                              set_features=None,
+                              expect_content=None,
+                              expect_source_name=None):
         testvm1 = self.app.add_new_vm(
             qubes.vm.appvm.AppVM,
             name=self.make_vm_name('vm1'), label='red')
@@ -483,6 +486,9 @@ async def _test_clipboard(self, test_string):
         await testvm2.create_on_disk()
         self.app.save()
 
+        for feature, value in (set_features or {}).items():
+            testvm1.features[feature] = value
+
         await asyncio.gather(
             testvm1.start(),
             testvm2.start())
@@ -514,18 +520,23 @@ async def _test_clipboard(self, test_string):
 
         clipboard_content = \
             open('/var/run/qubes/qubes-clipboard.bin', 'r').read().strip()
+
+        if expect_content is not None:
+            test_string = expect_content
         self.assertEqual(clipboard_content, test_string,
                           "Clipboard copy operation failed - content")
+        if expect_source_name is None:
+            expect_source_name = testvm1.name
         clipboard_source = \
             open('/var/run/qubes/qubes-clipboard.bin.source',
                  'r').read().strip()
-        self.assertEqual(clipboard_source, testvm1.name,
+        self.assertEqual(clipboard_source, expect_source_name,
                           "Clipboard copy operation failed - owner")
 
         # Then paste it to the other window
         window_title = 'user@{}'.format(testvm2.name)
         p = await testvm2.run(
-            'zenity --entry --title={} > /tmp/test.txt'.format(window_title))
+            'zenity --text-info --editable --title={} > /tmp/test.txt'.format(window_title))
         await self.wait_for_window_coro(window_title)
 
         subprocess.check_call(['xdotool', 'key', '--delay', '100',
@@ -553,6 +564,38 @@ def test_000_clipboard(self):
         test_string = "test123"
         self.loop.run_until_complete(self._test_clipboard(test_string))
 
+    @unittest.skipUnless(
+        spawn.find_executable('xdotool'),
+                         "xdotool not installed")
+    def test_001_clipboard_64k(self):
+        test_string = "test123abc" * 6400
+        self.loop.run_until_complete(self._test_clipboard(test_string))
+
+    @unittest.skipUnless(
+        spawn.find_executable('xdotool'),
+                         "xdotool not installed")
+    def test_002_clipboard_200k_truncated(self):
+        test_string = "test123abc" * 20000
+        self.loop.run_until_complete(self._test_clipboard(test_string,
+            expect_content="", expect_source_name=""))
+
+    @unittest.skipUnless(
+        spawn.find_executable('xdotool'),
+                         "xdotool not installed")
+    def test_002_clipboard_200k(self):
+        test_string = "test123abc" * 20000
+        self.loop.run_until_complete(self._test_clipboard(test_string,
+            set_features={"gui-max-clipboard-size": 200_000}))
+
+    @unittest.skipUnless(
+        spawn.find_executable('xdotool'),
+                         "xdotool not installed")
+    def test_002_clipboard_300k(self):
+        test_string = "test123abc" * 30000
+        self.loop.run_until_complete(self._test_clipboard(test_string,
+            expect_content="Qube clipboard size over 256KiB and X11 INCR "
+                           "protocol support is not implemented!"))
+
 
 class TC_05_StandaloneVMMixin(object):
     def setUp(self):