def test_observer_suspending():
rc = Context()
rc.new_value(v=1)
rc.new_expression('a', lambda env: env.v)
rc.new_observer('b', lambda env: env.a)
raises(Exception, rc.suspend, 'v')
raises(Exception, rc.suspend, 'a')
raises(Exception, rc.resume, 'v')
raises(Exception, rc.resume, 'a')
rc.suspend('b')
rc.run()
assert rc['a'].exec_count is 1
assert rc['b'].exec_count is 1
rc.resume('b')
rc.run()
assert rc['a'].exec_count is 1
assert rc['b'].exec_count is 1
rc.suspend('b')
assert not rc['b'].invalidated
rc.set_value(v=2)
assert rc['b'].invalidated
assert rc['a'].exec_count is 1
assert rc['b'].exec_count is 1
rc['b'].resume()
rc.set_value(v=2.5)
rc['b'].suspend()
rc.run()
assert rc['a'].exec_count is 2
assert rc['b'].exec_count is 2
rc.set_value(v=3)
assert rc['a'].exec_count is 2
assert rc['b'].exec_count is 2
assert rc['b'].invalidated
rc.set_value(v=4)
rc['b'].resume()
rc.run()
assert rc['a'].exec_count is 3
assert rc['b'].exec_count is 3
assert not rc['b'].invalidated
rc.suspend('b')
rc.set_value(v=5)
rc.resume('b', run=True)
assert rc['a'].exec_count is 4
assert rc['b'].exec_count is 4
