1 files changed, 41 insertions, 0 deletions
diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index b7d2b71c19..6976bd9742 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -506,4 +506,45 @@ class TestFiber < Test::Unit::TestCase
       GC.start
     RUBY
   end
+
+  def test_fiber_pool_stack_acquire_failure
+    environment = {
+      "RUBY_SHARED_FIBER_POOL_MINIMUM_COUNT" => "0",
+      "RUBY_SHARED_FIBER_POOL_MAXIMUM_COUNT" => "128"
+    }
+
+    # This program requires, effectively, at most one fiber stack, since the fiber immediately becomes unreachable.
+    assert_separately([environment], <<~RUBY, timeout: 30)
+      GC.disable
+      count_before = GC.count
+
+      # Create more fibers than the pool can handle (but they become immediately unreachable):
+      assert_nothing_raised do
+        256.times do
+          Fiber.new{Fiber.yield}.resume
+        end
+      end
+
+      # Major GC should have happened at least once:
+      assert_operator(GC.count, :>, count_before)
+    RUBY
+  end
+
+  def test_fiber_pool_stack_acquire_failure_at_maximum_count
+    environment = {
+      "RUBY_SHARED_FIBER_POOL_MAXIMUM_COUNT" => "128"
+    }
+
+    assert_separately([environment], <<~RUBY, timeout: 30)
+      GC.disable
+      fibers = []
+      assert_raise(FiberError) do
+        loop do
+          Fiber.new{fibers << Fiber.current; Fiber.yield}.resume
+          raise "expected FiberError before this" if fibers.size > 128
+        end
+      end
+      assert_operator fibers.size, :>=, 128
+    RUBY
+  end
 end