Issue #16655 has been reported by ko1 (Koichi Sasada).

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Feature #16655: Each test on test-all should run `srand(seed)` at setup
https://bugs.ruby-lang.org/issues/16655

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Target version: 2.8
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# Points

* call `srand($seed)` before each test. `$seed` is given seed number by `--seed N`

# Background

Some tests use `rand()` to produce random number to generate random test examples.

Example: 

```
  def test_local_variable_set_wb
    assert_ruby_status([], <<-'end;', '[Bug #13605]', timeout: 30)
      b = binding
      n = 20_000

      n.times do |i|
        v = rand(2_000)
        name = "n#{v}"
        value = Object.new
        b.local_variable_set name, value
      end
    end;
  end
```

This test generates 2,000 randomly named ivar which point random numbers.

However, several tests calls `srand(0)` and this random sequence is affected by test methods order.

Two problems:

* Test authors of this kind of tests should assume that every test processes uses very different random sequence to increase the test coverage.
* We can not get reproducible results on such tests which use random sequence with `--seed` because of `srand(0)` using tests.

# Proposal

To solve the above two problems, I`ll insert `srand($seed)` at the beginning of each test (`$seed` is given by `--seed` option).
This proposal respects `--seed` option more, so we can expect more deterministic results.

I measured performance overhead and I can't get meaningful slow down.

# Additional note

Surprisingly, `--seed` option is ignored just now on test-all, so I'll fix this problem too.




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