Check if signaled

test/ruby/test_fiber.rb

@@ -348,8 +348,10 @@ class TestFiber < Test::Unit::TestCase
     env = {}
     env['RUBY_FIBER_VM_STACK_SIZE'] = vm_stack_size.to_s if vm_stack_size
     env['RUBY_FIBER_MACHINE_STACK_SIZE'] = machine_stack_size.to_s if machine_stack_size
-    out, _ = Dir.mktmpdir("test_fiber") {|tmpdir|
-      EnvUtil.invoke_ruby([env, '-e', script], '', true, true, chdir: tmpdir, timeout: 30)
+    out = Dir.mktmpdir("test_fiber") {|tmpdir|
+      out, err, status = EnvUtil.invoke_ruby([env, '-e', script], '', true, true, chdir: tmpdir, timeout: 30)
+      assert(!status.signaled?, FailDesc[status, nil, err])
+      out
     }
     use_length ? out.length : out
   end