Add test coverage for auto-attestation skipping on non-rubygems.org hosts and JRuby

[Copilot]

What was the end-user or developer problem that led to this PR?

The auto-attestation feature in the push command has branching logic to skip attestation on JRuby and non-rubygems.org hosts, but test coverage only verified the happy path and error fallback. Missing tests for the conditional skipping paths.

What is your fix for the problem, implemented in this PR?

Added two test cases to verify auto-attestation is correctly skipped:

• test_execute_attestation_skipped_on_non_rubygems_host: Verifies attest! is not called when pushing to a private gem server. Uses allowed_push_host metadata to simulate a non-rubygems.org host, stubs attest! with a flag, and asserts raw application/octet-stream push succeeds.

• test_execute_attestation_skipped_on_jruby: Verifies attest! is not called on JRuby. Temporarily modifies RUBY_ENGINE constant to simulate JRuby environment, stubs attest! with a flag, and asserts raw push succeeds with proper cleanup in ensure block.

Both tests follow the existing pattern of using boolean flags with method stubs to track invocations, ensuring the branching logic in send_push_request works correctly.

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

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[Copilot]

Pull request overview

Adds missing test coverage for the push command’s auto-attestation branching logic, specifically the cases where attestation should be skipped on JRuby and when pushing to non-rubygems.org hosts.

Changes:

• Add a test asserting attest! is skipped when the gem’s allowed_push_host causes pushes to a non-rubygems.org host.
• Add a test asserting attest! is skipped when RUBY_ENGINE is jruby.

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[Copilot]

The attest! stub returns true, so if the code path regresses and attest! is invoked, the test will likely fail with an unrelated Gem.read_binary(true) type error before reaching the refute attest_called assertion. Consider making the stub explicitly fail (e.g., raising/flunking) to produce a clearer failure reason tied to the behavior being tested.

Suggested change

	@cmd.stub(:attest!, proc { attest_called = true }) do
	@cmd.stub(:attest!, proc {
	attest_called = true
	flunk "attest! should not be called for non-rubygems.org hosts"
	}) do

[Copilot]

RUBY_ENGINE is modified outside the begin/ensure region, so if an unexpected exception occurs during the constant swap, the original value may not be restored and could leak into other tests. Consider moving the constant swap inside the begin/ensure (or using the existing helper methods in test/rubygems/helper.rb that manage Ruby version/engine constants) to guarantee cleanup.

Suggested change

	engine = RUBY_ENGINE
	Object.send :remove_const, :RUBY_ENGINE
	Object.const_set :RUBY_ENGINE, "jruby"
	begin
	begin
	engine = RUBY_ENGINE
	Object.send :remove_const, :RUBY_ENGINE
	Object.const_set :RUBY_ENGINE, "jruby"

[Copilot]

Same issue as above: the attest! stub returns true, so if attest! is unexpectedly called this test will likely error out during request construction rather than failing with a clear assertion message. Prefer a stub that explicitly fails if invoked so the failure points directly at the regression.