# Copyright 2016 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Fake time, for testing."""
import six
class FakeTime(object):
"""Fake time, for testing."""
def __init__(self, chronology):
"""The chronology is a generator that updates the world.
Yield how many seconds of fake time elapse. Think of each yield as a
"sleep". We read the very first value immediately, so that the world can be
initialized in the chronology.
Args:
chronology: a generator that updates the state of the world and then
sleeps via yielding.
"""
self._chronology = chronology
# current fake time
self._now = 0
# time at which to wake up the chronology
self._next = six.advance_iterator(self._chronology)
def sleep(self, seconds):
"""Sleep for this many fictitious seconds.
The world will update accordingly.
Args:
seconds: how many seconds to pretend sleep for.
Raises:
IOError: for negative delays (matches time.sleep).
BaseException: at the end of times, to detect infinite loop bugs
and the like.
"""
if seconds < 0:
# Chosen to match the behavior of time.sleep.
raise IOError("Invalid argument")
target = self._now + seconds
if target < self._next:
self._now = target
return
self._now = target
for step in self._chronology:
self._next += step
if self._next > target:
return
raise BaseException("end of times")
def now(self):
"""Returns the current fake time."""
return self._now
