Add WeakSet edge case tests

[mrhapile]

This PR expands the WeakSet unit test coverage.

The initial WeakSet tests introduced basic behavioral tests.
#4912
This PR adds additional ECMAScript edge case coverage.

The following behaviors are now tested:

• Primitive rejection in WeakSet.prototype.add
• Primitive-safe behavior for WeakSet.prototype.has
• Primitive-safe behavior for WeakSet.prototype.delete
• Duplicate object additions

These tests ensure correct handling of ECMAScript §24.4 WeakSet
invariants and improve robustness during future refactors.

All tests follow the same pattern used by other builtin tests.

[Copilot]

Pull request overview

This PR expands Boa’s Rust-level unit tests for the WeakSet builtin to cover additional ECMAScript edge cases, improving regression protection beyond test262 coverage.

Changes:

• Adds a WeakSet builtin test module and wires it into weak_set/mod.rs.
• Introduces unit tests for primitive rejection in WeakSet.prototype.add, primitive-safe has/delete, and duplicate object additions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
core/engine/src/builtins/weak_set/tests.rs	Adds baseline + edge-case WeakSet behavior tests (add/has/delete, primitives, duplicates).
core/engine/src/builtins/weak_set/mod.rs	Includes the test module under #[cfg(test)].

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[Copilot]

The null case asserts an error message where the "got" type is object (because typeof null is "object"), which makes the message read like there was no type mismatch ("expected object … got object"). This makes the test misleading/brittle and also locks in a confusing engine error string. Consider either (a) updating the WeakSet.add TypeError message to special-case null (e.g., report null explicitly) and then adjusting this assertion accordingly, or (b) changing this test to assert only that a TypeError is thrown for null without coupling to the exact message text.

Suggested change

	TestAction::assert_native_error(
	"ws.add(null);",
	JsNativeErrorKind::Type,
	"WeakSet.add: expected target argument of type `object`, got target of type `object`",
	TestAction::assert(
	"try { ws.add(null); false } catch (e) { e instanceof TypeError }",

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	49,666	49,666	0
Ignored	2,284	2,284	0
Failed	1,013	1,013	0
Panics	0	0	0
Conformance	93.77%	93.77%	0.00%

Tested main commit: 1753d9729e3d0930d808990f6911ca0b940a21d7
Tested PR commit: e7fdf7de78ed9c57e189fd2f132b80a6b88fc77b
Compare commits: 1753d97...e7fdf7d

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.78%. Comparing base (6ddc2b4) to head (e7fdf7d).
⚠️ Report is 772 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #4914       +/-   ##
===========================================
+ Coverage   47.24%   57.78%   +10.54%     
===========================================
  Files         476      556       +80     
  Lines       46892    60739    +13847     
===========================================
+ Hits        22154    35101    +12947     
- Misses      24738    25638      +900     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.