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Elixir: Simple implementation of `assert_eventually` for tests
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@default_interval 99 | |
@default_timeout 9_000 | |
@doc """ | |
Assert that a condition eventually evaluates to `true`. | |
## Options | |
All time-related options are in milliseconds. | |
- `:timeout` (default: `#{@default_timeout}`) - the maximum total time until the assertion fails | |
- `:interval` (default: `#{@default_interval}`) - how long to wait between attempts | |
## Examples | |
iex> assert_eventually(fn -> Enum.random([0, 2, 3]) == 3 end) | |
true | |
Keep trying every 0 second for a maximum of 30 seconds: | |
iex> assert_eventually(fn -> Enum.random([0, 2]) == 3 end, timeout: 30_000, interval: 1_000) | |
%ExUnit.AssertionError{} | |
""" | |
def assert_eventually(func, opts \\ []) do | |
timeout = Keyword.get(opts, :timeout, @default_timeout) | |
interval = Keyword.get(opts, :interval, @default_interval) | |
number_of_attempts = timeout |> div(interval) | |
assert Enum.reduce_while(0..number_of_attempts, _acc = nil, fn _x, _acc -> | |
:timer.sleep(interval) | |
if func.() == true, | |
do: {:halt, true}, | |
else: {:cont, false} | |
end) | |
end |
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