From 00db7dd1f1730ded2d493fd11d31f63807534393 Mon Sep 17 00:00:00 2001
From: nick evans <nick@rubinick.dev>
Date: Sun, 19 Jul 2026 12:34:27 -0400
Subject: [PATCH] =?UTF-8?q?=E2=9C=85=20Fix=20JRuby=20local=20backtrace=20t?=
 =?UTF-8?q?est=20assertions?=
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A bug was fixed in jruby-head, but that may not be in current releases:
* JRuby Issue: jruby/jruby#9528
* Fixed by: jruby/jruby#9528

With that issue fixed, these tests don't need to be marked pending! 😄

BUT, JRuby _does_ still have some incongruity between `caller(1)` and
`raise rescue $!.backtrace[1..]`.  Some ruby block stack frames in
`caller` are replaced by java stack frames in `Exception#backtrace`.
For example:

```diff
--- Kernel#caller
+++ Exception#backtrace
  /home/nick/.local/share/rubies/jruby-dev/lib/ruby/gems/shared/gems/test-unit-3.7.8/lib/test/unit/testcase.rb:632:in 'block in run'
- /home/nick/.local/share/rubies/jruby-dev/lib/ruby/gems/shared/gems/test-unit-3.7.8/lib/test/unit/testcase.rb:631:in 'catch'
+ org/jruby/RubyKernel.java:1604:in 'catch'
+ org/jruby/RubyKernel.java:1599:in 'catch'
  /home/nick/.local/share/rubies/jruby-dev/lib/ruby/gems/shared/gems/test-unit-3.7.8/lib/test/unit/testcase.rb:631:in 'run'
```

The workaround is relatively simple: use a locally generated exception
to generate the stack frames for comparison.
---
 test/lib/helper.rb             | 17 +++++++++++++++--
 test/net/imap/test_imap_tls.rb |  2 +-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/test/lib/helper.rb b/test/lib/helper.rb
index fe11727d..e52a1e19 100644
--- a/test/lib/helper.rb
+++ b/test/lib/helper.rb
@@ -224,11 +224,24 @@ def assert_local_raise(expected, message = nil)
     else
       assert_raise(expected, &block)
     end
-    stack = caller
-    assert_equal stack, error.backtrace&.last(stack.size)
+    assert_local_backtrace error
     error
   end
 
+  # Asserts that +error+ was raised in the same thread as +caller+ _and_ was
+  # called from the same level as +caller+.  The caller's own frame is ignored,
+  # as are all extra frames in +error+, but the remaining frames much match.
+  #
+  # NOTE: `stack = caller(2)` is different from `$!.backtrace[2..]` in JRuby.
+  # Rather than use `caller`, this raises a local exception to use its backtrace
+  # for the comparison.
+  def assert_local_backtrace(error)
+    local_stack = raise "generating local backtrace" rescue $!.backtrace[2..]
+    error_stack = error.backtrace&.last(local_stack.size)
+    assert_equal local_stack, error_stack
+    error_stack
+  end
+
   # Combines +assert_local_raise+ with an assertion that the exception's cause
   # is in the receiver thread.
   #
diff --git a/test/net/imap/test_imap_tls.rb b/test/net/imap/test_imap_tls.rb
index 052c114e..0fbceed8 100644
--- a/test/net/imap/test_imap_tls.rb
+++ b/test/net/imap/test_imap_tls.rb
@@ -110,7 +110,7 @@ def test_starttls_unknown_ca
         imap
       end
       assert_kind_of(OpenSSL::SSL::SSLError, ex)
-      assert_equal (stack = caller), ex.backtrace&.last(stack.size)
+      assert_local_backtrace ex
       assert_equal false, imap.tls_verified?
       assert_equal({}, imap.ssl_ctx_params)
       assert_equal(nil, imap.ssl_ctx.ca_file)