diff -r 1ec5ce21cb46 -r 01361be9e2dc tests/test-wireproto-clientreactor.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-wireproto-clientreactor.py	Mon Apr 09 15:32:01 2018 -0700
@@ -0,0 +1,66 @@
+from __future__ import absolute_import
+
+import unittest
+
+from mercurial import (
+    error,
+    wireprotoframing as framing,
+)
+
+class SingleSendTests(unittest.TestCase):
+    """A reactor that can only send once rejects subsequent sends."""
+    def testbasic(self):
+        reactor = framing.clientreactor(hasmultiplesend=False, buffersends=True)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        self.assertEqual(request.state, 'pending')
+        self.assertEqual(action, 'noop')
+
+        action, meta = reactor.flushcommands()
+        self.assertEqual(action, 'sendframes')
+
+        for frame in meta['framegen']:
+            self.assertEqual(request.state, 'sending')
+
+        self.assertEqual(request.state, 'sent')
+
+        with self.assertRaisesRegexp(error.ProgrammingError,
+                                     'cannot issue new commands'):
+            reactor.callcommand(b'foo', {})
+
+        with self.assertRaisesRegexp(error.ProgrammingError,
+                                     'cannot issue new commands'):
+            reactor.callcommand(b'foo', {})
+
+class NoBufferTests(unittest.TestCase):
+    """A reactor without send buffering sends requests immediately."""
+    def testbasic(self):
+        reactor = framing.clientreactor(hasmultiplesend=True, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'command1', {})
+        self.assertEqual(request.requestid, 1)
+        self.assertEqual(action, 'sendframes')
+
+        self.assertEqual(request.state, 'pending')
+
+        for frame in meta['framegen']:
+            self.assertEqual(request.state, 'sending')
+
+        self.assertEqual(request.state, 'sent')
+
+        action, meta = reactor.flushcommands()
+        self.assertEqual(action, 'noop')
+
+        # And we can send another command.
+        request, action, meta = reactor.callcommand(b'command2', {})
+        self.assertEqual(request.requestid, 3)
+        self.assertEqual(action, 'sendframes')
+
+        for frame in meta['framegen']:
+            self.assertEqual(request.state, 'sending')
+
+        self.assertEqual(request.state, 'sent')
+
+if __name__ == '__main__':
+    import silenttestrunner
+    silenttestrunner.main(__name__)