From 28d0e1ed4acd252b4ce20cae411ec4fc060407da Mon Sep 17 00:00:00 2001
From: Rafael Fourquet <fourquet.rafael@gmail.com>
Date: Sun, 17 Sep 2023 17:43:49 +0200
Subject: [PATCH] TaskLocalRNG: test that `copy` handles the splitmix state
 (#51355)

This adds a test for #51332.
---
 stdlib/Random/test/runtests.jl | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/stdlib/Random/test/runtests.jl b/stdlib/Random/test/runtests.jl
index 3f570d862b743..94749b12123c3 100644
--- a/stdlib/Random/test/runtests.jl
+++ b/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