Randomized test for String.grapheme/1 failed on main #12165
Description
Elixir and Erlang/OTP versions
Latest main
Erlang/OTP 25 [erts-13.0] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]
Elixir 1.15.0-dev (8cb3426) (compiled with Erlang/OTP 25)
Operating system
macOS 12.4
Current behavior
This randomized test failed on my local:
1) test next_grapheme/1 (StringTest)
test/elixir/string_test.exs:585
** (ArgumentError) argument error
code: for _ <- 1..10 do
stacktrace:
:erlang.++([169 | <<246, 64, 171, 154, 65, 19, 36, 158, 149, 178, 14, 30, 207, 173, 107, 0, 158, 226, 147, 219, 216, 205, 41, 36, 210, 58, 180, 125, 221, 110, 143, 48, 16, 140, 197, 61, 57, 234, 234, 35, 242, 4, 247, 230, 125, 234, 117, 199, 126, ...>>], [<<246, 64, 171, 154, 65, 19, 36, 158, 149, 178, 14, 30, 207, 173, 107, 0, 158, 226, 147, 219, 216, 205, 41, 36, 210, 58, 180, 125, 221, 110, 143, 48, 16, 140, 197, 61, 57, 234, 234, 35, 242, 4, 247, 230, 125, 234, 117, 199, 126, ...>>])
(stdlib 4.0) unicode_util.erl:3168: :unicode_util.gc_ext_pict/3
(elixir 1.15.0-dev) lib/string.ex:1931: String.next_grapheme/1
(elixir 1.15.0-dev) lib/stream.ex:1740: Stream.do_unfold/4
(elixir 1.15.0-dev) lib/enum.ex:375: Enum.all?/2
test/elixir/string_test.exs:592: anonymous fn/2 in StringTest."test next_grapheme/1"/1
(elixir 1.15.0-dev) lib/enum.ex:4299: Enum.reduce_range/5
test/elixir/string_test.exs:589: (test)Expected behavior
Never fail?
Maybe it would be nice to have a prop-based test for this as well, I will open a PR to stream_data to add one.