1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
import asyncio
import contextlib
from websockets.asyncio.connection import Connection
class InterceptingConnection(Connection):
"""
Connection subclass that can intercept outgoing packets.
By interfacing with this connection, we simulate network conditions
affecting what the component being tested receives during a test.
"""
def connection_made(self, transport):
super().connection_made(InterceptingTransport(transport))
@contextlib.contextmanager
def delay_frames_sent(self, delay):
"""
Add a delay before sending frames.
This can result in out-of-order writes, which is unrealistic.
"""
assert self.transport.delay_write is None
self.transport.delay_write = delay
try:
yield
finally:
self.transport.delay_write = None
@contextlib.contextmanager
def delay_eof_sent(self, delay):
"""
Add a delay before sending EOF.
This can result in out-of-order writes, which is unrealistic.
"""
assert self.transport.delay_write_eof is None
self.transport.delay_write_eof = delay
try:
yield
finally:
self.transport.delay_write_eof = None
@contextlib.contextmanager
def drop_frames_sent(self):
"""
Prevent frames from being sent.
Since TCP is reliable, sending frames or EOF afterwards is unrealistic.
"""
assert not self.transport.drop_write
self.transport.drop_write = True
try:
yield
finally:
self.transport.drop_write = False
@contextlib.contextmanager
def drop_eof_sent(self):
"""
Prevent EOF from being sent.
Since TCP is reliable, sending frames or EOF afterwards is unrealistic.
"""
assert not self.transport.drop_write_eof
self.transport.drop_write_eof = True
try:
yield
finally:
self.transport.drop_write_eof = False
class InterceptingTransport:
"""
Transport wrapper that intercepts calls to ``write()`` and ``write_eof()``.
This is coupled to the implementation, which relies on these two methods.
Since ``write()`` and ``write_eof()`` are not coroutines, this effect is
achieved by scheduling writes at a later time, after the methods return.
This can easily result in out-of-order writes, which is unrealistic.
"""
def __init__(self, transport):
self.loop = asyncio.get_running_loop()
self.transport = transport
self.delay_write = None
self.delay_write_eof = None
self.drop_write = False
self.drop_write_eof = False
def __getattr__(self, name):
return getattr(self.transport, name)
def write(self, data):
if not self.drop_write:
if self.delay_write is not None:
self.loop.call_later(self.delay_write, self.transport.write, data)
else:
self.transport.write(data)
def write_eof(self):
if not self.drop_write_eof:
if self.delay_write_eof is not None:
self.loop.call_later(self.delay_write_eof, self.transport.write_eof)
else:
self.transport.write_eof()
|
