Just let the test use the real SFTPServer service

src/allmydata/client.py

@@ -1071,7 +1071,7 @@ class _Client(node.Node, pollmixin.PollMixin):
             if accountfile:
                 accountfile = self.config.get_config_path(accountfile)
             accounturl = self.config.get_config("sftpd", "accounts.url", None)
-            sftp_portstr = self.config.get_config("sftpd", "port", "8022")
+            sftp_portstr = self.config.get_config("sftpd", "port", "tcp:8022")
             pubkey_file = self.config.get_config("sftpd", "host_pubkey_file")
             privkey_file = self.config.get_config("sftpd", "host_privkey_file")
 

src/allmydata/frontends/sftpd.py

@@ -1975,6 +1975,8 @@ class Dispatcher(object):
 
 
 class SFTPServer(service.MultiService):
+    name = "frontend:sftp"
+
     def __init__(self, client, accountfile, accounturl,
                  sftp_portstr, pubkey_file, privkey_file):
         precondition(isinstance(accountfile, (unicode, NoneType)), accountfile)

src/allmydata/test/data/openssh-rsa-2048

@@ -0,0 +1,27 @@
+-----BEGIN OPENSSH PRIVATE KEY-----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+-----END OPENSSH PRIVATE KEY-----

src/allmydata/test/data/openssh-rsa-2048.pub

@@ -0,0 +1 @@
+ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDx5JfaPwE2wfXIQcmlGte9EPAbrTmHPGOF/PuZ71XPa3mZTHMQQuc959gmLxupmcc5o4jYe8VTwT6bbNl6YM+HmCvL3XVH0BqdM2lpKCTB/WzSAyFUv8gSjQVXekRm9wF69tZkPrudqutTLhqXU5ESiUzfhU+CxHQW+kAf10Yd9R68V1f8jkuWjEoeVfCltj7O5fRlpouoTXn83MUAXB3J/wDjpjnjp2PxvXL2x5aCHtzd1WCGEmtWbHZvRA1a0EE233zfXNHg4xLd3ycUqAxoRlCcC230itUBXtr4qgDMzRdsL+HGWrcJ+4yezlQj+l8mc7vi5shNT7HDRfvi/rE7 exarkun@baryon

src/allmydata/test/test_client.py

@@ -1,5 +1,4 @@
 import os, sys
-import mock
 from functools import (
     partial,
 )
@@ -422,19 +421,32 @@ class Basic(testutil.ReallyEqualMixin, unittest.TestCase):
         """
         configuration for sftpd results in it being started
         """
+        root = FilePath(self.mktemp())
+        root.makedirs()
+        accounts = root.child(b"sftp-accounts")
+        accounts.touch()
+
+        data = FilePath(__file__).sibling(b"data")
+        privkey = data.child(b"openssh-rsa-2048")
+        pubkey = data.child(b"openssh-rsa-2048.pub")
+
         basedir = u"client.Basic.test_ftp_create"
         create_node_dir(basedir, "testing")
         with open(os.path.join(basedir, "tahoe.cfg"), "w") as f:
-            f.write(
+            f.write((
                 '[sftpd]\n'
                 'enabled = true\n'
-                'accounts.file = foo\n'
-                'host_pubkey_file = pubkey\n'
-                'host_privkey_file = privkey\n'
-            )
-        with mock.patch('allmydata.frontends.sftpd.SFTPServer') as p:
-            yield client.create_client(basedir)
-        self.assertTrue(p.called)
+                'accounts.file = {}\n'
+                'host_pubkey_file = {}\n'
+                'host_privkey_file = {}\n'
+            ).format(accounts.path, pubkey.path, privkey.path))
+
+        client_node = yield client.create_client(
+            basedir,
+        )
+        sftp = client_node.getServiceNamed("frontend:sftp")
+        self.assertIs(sftp.parent, client_node)
+
 
     @defer.inlineCallbacks
     def test_ftp_auth_keyfile(self):