feat: improve codegen testing and add verify target

- Add `make verify` for fast local validation suite
- Add AGENTS.md with repository guidelines for AI assistants
- Fix rust_writer.py: check for existing `impl Solution` before generating
- Refactor test_code_generation.py: align with dev snippet fixture, add design problem test

Author: QuBenhao

AGENTS.md

@@ -0,0 +1,35 @@
+# Repository Guidelines
+
+## Project Structure & Module Organization
+
+This repository stores LeetCode solutions, local runners, and code-generation tooling across several languages. Problem folders live under `problems/problems_<id>/` and usually contain `problem.md`, `problem_zh.md`, `solution.*`, `Solution.*`, `solution.md`, and testcase files. Shared language helpers are in `python/`, `golang/`, `typescript/`, `cpp/`, and `rust/`; reusable algorithm notes are in `algorithm_templates/`; metadata is in `data/`; automated tests are in `tests/`. Multithreading problems have their own layout under `multi_threading/<id>/`.
+
+## Build, Test, and Development Commands
+
+- `make verify`: run stable local checks across Python codegen/unit tests, TypeScript smoke tests, and Go helper packages.
+- `make test`: run the full Python pytest suite with `PYTHONPATH=.`.
+- `make test-unit`: run fast unit tests marked `unit`.
+- `make test-integration`: run integration tests that may require language runtimes.
+- `make test-codegen`: validate code generation behavior.
+- `make test-coverage`: run pytest with terminal and HTML coverage reports.
+- `npm test`: run the full TypeScript/Jest suite through `ts-jest`.
+- `make test-go-libs`: run stable Go helper package tests.
+- `python python/scripts/leetcode.py`: launch the interactive LeetCode helper for fetching/submitting problems.
+
+Use `make help` for the maintained command list.
+
+## Coding Style & Naming Conventions
+
+Follow the style of the target language and existing generated files. Python uses pytest-compatible modules and 4-space indentation. Go code should be `gofmt` formatted. TypeScript uses lowercase filenames in `typescript/` and Jest test files such as `debug.test.ts`. Problem directories use `problems_<id>` naming, with language-specific solution names like `solution.py`, `solution.go`, `solution.ts`, `solution.rs`, `Solution.cpp`, and `Solution.java`.
+
+## Testing Guidelines
+
+Pytest discovers `test_*.py` and `*_test.py` under `tests/`; test classes start with `Test`, and test functions start with `test_`. Use markers from `pytest.ini`: `unit`, `integration`, `codegen`, and `slow`. For problem-level validation, run `make test-daily`, `make test-problems`, or the relevant language command. Add focused tests when changing code generation, language writers, shared models, or testcase parsing.
+
+## Commit & Pull Request Guidelines
+
+Recent commits use short prefixes such as `test:` and `fix:`; examples include `test: 3742 solution`, `test: [20260430] Add (3742)`, and `fix: 题解链接bug`. Keep messages imperative or descriptive, scoped to one change. Pull requests should summarize changed problems or tooling, list test commands run, mention required environment variables, and link related issues when applicable. Include screenshots only for documentation or UI-facing changes.
+
+## Security & Configuration Tips
+
+Do not commit `.env`, LeetCode cookies, PushDeer keys, or other secrets. Required local values include `COOKIE`, `PROBLEM_FOLDER`, `LANGUAGES`, `LEETCODE_USER`, and `PYTHONPATH=.`; see `README.md` for an example configuration.

Makefile

@@ -1,16 +1,19 @@
 # Makefile for LeetCode project
 
-.PHONY: test test-unit test-integration test-codegen test-coverage clean help
+.PHONY: verify test test-unit test-integration test-codegen test-coverage test-typescript-smoke test-go-libs clean help
 
 # Default target
 help:
 	@echo "Available targets:"
+	@echo "  verify            - Run the practical local verification suite"
 	@echo "  test              - Run all tests"
 	@echo "  test-unit         - Run unit tests only"
 	@echo "  test-integration  - Run integration tests (requires language runtimes)"
 	@echo "  test-codegen      - Run code generation tests"
 	@echo "  test-coverage     - Run tests with coverage report"
 	@echo "  test-parallel     - Run tests in parallel"
+	@echo "  test-typescript-smoke - Run stable TypeScript smoke tests"
+	@echo "  test-go-libs      - Run stable Go helper package tests"
 	@echo "  test-daily        - Run daily problem test (current problem)"
 	@echo "  test-problems     - Run multiple problems test"
 	@echo "  clean             - Clean up temporary files"
@@ -20,6 +23,12 @@ help:
 	@echo "  add-snippet       - Add a problem to snippets (use PROBLEM=id)"
 	@echo "  print-snippet     - Print original snippet (use PROBLEM=id LANG=lang)"
 
+# Run the practical local verification suite
+verify:
+	PYTHONPATH=. pytest tests/ -m "(unit or codegen) and not slow" -v
+	npm test -- --runTestsByPath typescript/debug.test.ts
+	go test ./golang/models ./golang/node_random ./golang/node_neighbours ./golang/tree_next ./golang/double_linked_node_child
+
 # Run all unit tests
 test-unit:
 	PYTHONPATH=. pytest tests/ -m unit -v
@@ -44,6 +53,14 @@ test-coverage:
 test-parallel:
 	PYTHONPATH=. pytest tests/ -v -n auto
 
+# Run stable TypeScript smoke tests
+test-typescript-smoke:
+	npm test -- --runTestsByPath typescript/debug.test.ts
+
+# Run stable Go helper package tests
+test-go-libs:
+	go test ./golang/models ./golang/node_random ./golang/node_neighbours ./golang/tree_next ./golang/double_linked_node_child
+
 # Run daily problem test
 test-daily:
 	PYTHONPATH=. python python/test.py

python/lc_libs/rust_writer.py

@@ -74,7 +74,7 @@ def write_solution(
         if not RustWriter.is_snake_case(f"{problem_folder}_{problem_id}"):
             add_title = f"#![allow(non_snake_case)]\n"
         code = code or code_default
-        if "object will be instantiated and called as such:" in code:
+        if "object will be instantiated and called as such:" in code and "impl Solution" not in code:
             struct_map = RustWriter._parse_rust_structs(code_default)
             solve_part = RustWriter._generate_solve_function(struct_map)
             return SOLUTION_TEMPLATE_RUST.format(add_title, "\n".join([]), "",

tests/test_code_generation.py

@@ -28,6 +28,15 @@
 # Languages that are fully supported
 SUPPORTED_LANGUAGES = ["python3", "cpp", "java", "typescript", "golang", "rust"]
 
+# These cases are intentionally sourced from python/dev/question_code_snippets.json.
+# Keep them aligned with that fixture so targeted codegen tests do not silently skip.
+DEV_SNIPPET_CASES = {
+    "simple": "1",
+    "list_node": "23",
+    "tree_node": "919",
+    "design": "1656",
+}
+
 
 def get_writer(lang_slug: str) -> Optional[lc_libs.LanguageWriter]:
     """Get the Writer instance for a language slug."""
@@ -40,6 +49,14 @@ def get_writer(lang_slug: str) -> Optional[lc_libs.LanguageWriter]:
     return cls()
 
 
+def get_problem_snippets(question_snippets: List[Dict[str, Any]], problem_id: str) -> List[Dict[str, Any]]:
+    """Return snippet records for a problem that must exist in the dev fixture."""
+    for item in question_snippets:
+        if problem_id in item:
+            return item[problem_id]
+    raise AssertionError(f"Problem {problem_id} not found in python/dev/question_code_snippets.json")
+
+
 class TestCodeGeneration:
     """Tests for code generation across languages."""
 
@@ -68,17 +85,8 @@ def test_writer_has_solution_file(self, lang_slug: str):
     @pytest.mark.codegen
     def test_generate_simple_two_sum(self, question_snippets: List[Dict[str, Any]], temp_dir: Path):
         """Test code generation for Two Sum problem (simple function signature)."""
-        problem_id = "1"
-        problem_data = None
-
-        # Find Two Sum in snippets
-        for item in question_snippets:
-            if problem_id in item:
-                problem_data = item[problem_id]
-                break
-
-        if problem_data is None:
-            pytest.skip(f"Problem {problem_id} not found in snippets")
+        problem_id = DEV_SNIPPET_CASES["simple"]
+        problem_data = get_problem_snippets(question_snippets, problem_id)
 
         for code_snippet in problem_data:
             lang_slug = code_snippet.get("langSlug", "")
@@ -105,17 +113,8 @@ def test_generate_simple_two_sum(self, question_snippets: List[Dict[str, Any]],
     @pytest.mark.codegen
     def test_generate_tree_node_problem(self, question_snippets: List[Dict[str, Any]], temp_dir: Path):
         """Test code generation for a TreeNode problem."""
-        # Problem 226: Invert Binary Tree
-        problem_id = "226"
-        problem_data = None
-
-        for item in question_snippets:
-            if problem_id in item:
-                problem_data = item[problem_id]
-                break
-
-        if problem_data is None:
-            pytest.skip(f"Problem {problem_id} not found in snippets")
+        problem_id = DEV_SNIPPET_CASES["tree_node"]
+        problem_data = get_problem_snippets(question_snippets, problem_id)
 
         for code_snippet in problem_data:
             lang_slug = code_snippet.get("langSlug", "")
@@ -143,17 +142,8 @@ def test_generate_tree_node_problem(self, question_snippets: List[Dict[str, Any]
     @pytest.mark.codegen
     def test_generate_list_node_problem(self, question_snippets: List[Dict[str, Any]], temp_dir: Path):
         """Test code generation for a ListNode problem."""
-        # Problem 206: Reverse Linked List
-        problem_id = "206"
-        problem_data = None
-
-        for item in question_snippets:
-            if problem_id in item:
-                problem_data = item[problem_id]
-                break
-
-        if problem_data is None:
-            pytest.skip(f"Problem {problem_id} not found in snippets")
+        problem_id = DEV_SNIPPET_CASES["list_node"]
+        problem_data = get_problem_snippets(question_snippets, problem_id)
 
         for code_snippet in problem_data:
             lang_slug = code_snippet.get("langSlug", "")
@@ -179,18 +169,43 @@ def test_generate_list_node_problem(self, question_snippets: List[Dict[str, Any]
                 pytest.skip(f"Language {lang_slug} not fully implemented: {e}")
 
     @pytest.mark.codegen
-    @pytest.mark.slow
-    def test_generate_all_snippets(self, question_snippets: List[Dict[str, Any]]):
-        """Test code generation for all problems in snippets.
+    def test_generate_design_problem(self, question_snippets: List[Dict[str, Any]], temp_dir: Path):
+        """Test code generation for a class/design problem from the dev snippets."""
+        problem_id = DEV_SNIPPET_CASES["design"]
+        problem_data = get_problem_snippets(question_snippets, problem_id)
+
+        for code_snippet in problem_data:
+            lang_slug = code_snippet.get("langSlug", "")
+            if lang_slug not in SUPPORTED_LANGUAGES:
+                continue
+
+            writer = get_writer(lang_slug)
+            if writer is None:
+                continue
+
+            try:
+                generated = writer.write_solution(
+                    code_snippet["code"],
+                    None,
+                    format_question_id(problem_id),
+                    "problems"
+                )
+                assert generated, f"Generated code should not be empty for {lang_slug}"
+                assert "orderedstream" in generated.lower() and "insert" in generated, \
+                    f"Generated code should preserve design/class structure for {lang_slug}"
+            except NotImplementedError as e:
+                pytest.skip(f"Language {lang_slug} not fully implemented: {e}")
 
-        This is a comprehensive test that validates all code snippets.
-        Marked as slow, run with: pytest -m slow
-        """
+    @pytest.mark.codegen
+    def test_generate_all_snippets(self, question_snippets: List[Dict[str, Any]]):
+        """Test code generation for all supported snippets in python/dev."""
         errors = []
         generated_count = {}
+        problems_seen = set()
 
         for item in question_snippets:
             for problem_id, code_list in item.items():
+                problems_seen.add(problem_id)
                 for code_snippet in code_list:
                     lang_slug = code_snippet.get("langSlug", "")
                     if lang_slug not in SUPPORTED_LANGUAGES:
@@ -214,14 +229,12 @@ def test_generate_all_snippets(self, question_snippets: List[Dict[str, Any]]):
                     except Exception as e:
                         errors.append(f"Problem {problem_id} ({lang_slug}): {type(e).__name__}: {e}")
 
-        # Log summary
         print(f"\nCode generation summary: {generated_count}")
 
-        # Allow some errors but report them
+        assert problems_seen, "No problems found in python/dev/question_code_snippets.json"
+        assert generated_count, "No supported snippets generated from python/dev/question_code_snippets.json"
         if errors:
-            error_rate = len(errors) / max(sum(generated_count.values()), 1)
-            if error_rate > 0.1:  # More than 10% failure rate
-                pytest.fail(f"Too many code generation failures:\n" + "\n".join(errors[:10]))
+            pytest.fail("Code generation failures:\n" + "\n".join(errors[:20]))
 
 
 class TestWriterEnvironment:
@@ -304,4 +317,4 @@ def test_resolve_circular_link(self, tmp_path: Path):
             json.dump({"link_to": "1", "link_folder": "problems"}, f)
 
         with pytest.raises(ValueError, match="Circular link"):
-            LanguageWriter._resolve_link(problem_1)
+            LanguageWriter._resolve_link(problem_1)