TaskLocalRNG: test that copy handles the splitmix state (JuliaLang#…

…51355)

This adds a test for JuliaLang#51332.

stdlib/Random/test/runtests.jl

@@ -1065,3 +1065,26 @@ end
  end
  end
 end
+
+@testset "TaskLocalRNG: copy and copy! handle the splitmix state" begin
+ seeds = rand(RandomDevice(), UInt64, 5)
+ for seed in seeds
+ Random.seed!(seed)
+ rng1 = copy(TaskLocalRNG())
+ x = fetch(@async rand(UInt64))
+ rng2 = copy(TaskLocalRNG())
+ y = fetch(@async rand(UInt64))
+ rng3 = copy(TaskLocalRNG())
+ @test x != y
+ @test rng1 != rng2
+ Random.seed!(seed)
+ @test TaskLocalRNG() == rng1
+ @test x == fetch(@async rand(UInt64))
+ @test TaskLocalRNG() == rng2
+ # this should be a no-op:
+ copy!(TaskLocalRNG(), copy(TaskLocalRNG()))
+ @test TaskLocalRNG() == rng2
+ @test y == fetch(@async rand(UInt64))
+ @test TaskLocalRNG() == rng3
+ end
+end