make tests more stable #1105

Job	Run time
static analysis (Elixir 1.15.x \| Erlang/OTP 25.x)	22s
mix test windows (Elixir 1.13.x \| Erlang/OTP 22.x)	6m 47s
mix test (Elixir 1.12.x \| Erlang/OTP 22.x)	5m 2s
mix test windows (Elixir 1.13.x \| Erlang/OTP 23.x)	6m 25s
mix test (Elixir 1.12.x \| Erlang/OTP 23.x)	5m 28s
mix test windows (Elixir 1.13.x \| Erlang/OTP 24.x)	4m 59s
mix test (Elixir 1.12.x \| Erlang/OTP 24.x)	3m 48s
mix test windows (Elixir 1.13.x \| Erlang/OTP 25.x)	4m 14s
mix test (Elixir 1.13.x \| Erlang/OTP 22.x)	4m 7s
mix test windows (Elixir 1.14.x \| Erlang/OTP 23.x)	6m 28s
mix test (Elixir 1.13.x \| Erlang/OTP 23.x)	4m 38s
mix test windows (Elixir 1.14.x \| Erlang/OTP 24.x)	5m 9s
mix test (Elixir 1.13.x \| Erlang/OTP 24.x)	3m 15s
mix test windows (Elixir 1.14.x \| Erlang/OTP 25.x)	4m 23s
mix test (Elixir 1.13.x \| Erlang/OTP 25.x)	3m 10s
mix test (Elixir 1.14.x \| Erlang/OTP 23.x)	4m 45s
mix test (Elixir 1.14.x \| Erlang/OTP 24.x)	4m 19s
mix test windows (Elixir 1.14.x \| Erlang/OTP 26.x)	4m 32s
mix test (Elixir 1.14.x \| Erlang/OTP 25.x)	3m 6s
mix test windows (Elixir 1.15.x \| Erlang/OTP 24.x)	5m 1s
mix test (Elixir 1.14.x \| Erlang/OTP 26.x)	3m 5s
mix test windows (Elixir 1.15.x \| Erlang/OTP 25.x)	4m 29s
mix test (Elixir 1.15.x \| Erlang/OTP 24.x)	3m 24s
mix test windows (Elixir 1.15.x \| Erlang/OTP 26.x)	4m 57s
mix test (Elixir 1.15.x \| Erlang/OTP 25.x)	3m 2s
mix test (Elixir 1.15.x \| Erlang/OTP 26.x)	3m 3s
	1h 51m 58s

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