Feature #16655
Updated by ko1 (Koichi Sasada) almost 5 years ago
# 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 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.