test: add 23 tests for /repos/analyze endpoint + IndexConfig validation

Test coverage:
- URL regex: standard, trailing slash, http, rejects non-github/subpaths/no-repo
- AnalyzeRepoRequest: valid, whitespace strip, rejects empty/non-github
- IndexConfig: valid paths, slash normalization, backslash normalization,
  rejects empty/traversal/nested-traversal/non-string, allows None
- _fetch_directory_tree: flat repo grouping, monorepo package-level grouping,
  node_modules skipping, large_repo suggestion, small repo no suggestion

Also manually verified on Effect-TS/effect (1,767 files, 33 packages,
correct monorepo grouping at packages/* level).

23/23 pass in 2.8s.

Author: DevanshuNEU

backend/tests/test_analyze_repo.py

@@ -0,0 +1,208 @@
+"""Tests for POST /repos/analyze -- pre-clone directory analysis (OPE-109)."""
+import pytest
+from unittest.mock import AsyncMock, patch, MagicMock
+
+# Import after conftest patches external services
+from routes.repos import (
+    _fetch_directory_tree,
+    _GITHUB_URL_RE,
+    AnalyzeRepoRequest,
+    IndexConfig,
+)
+
+
+# -- URL regex tests ----------------------------------------------------------
+
+class TestGitHubUrlRegex:
+    def test_standard_url(self):
+        match = _GITHUB_URL_RE.match("https://github.com/Effect-TS/effect")
+        assert match is not None
+        assert match.group("owner") == "Effect-TS"
+        assert match.group("repo") == "effect"
+
+    def test_url_with_trailing_slash(self):
+        match = _GITHUB_URL_RE.match("https://github.com/owner/repo/")
+        assert match is not None
+
+    def test_http_url(self):
+        match = _GITHUB_URL_RE.match("http://github.com/owner/repo")
+        assert match is not None
+
+    def test_rejects_non_github(self):
+        assert _GITHUB_URL_RE.match("https://gitlab.com/owner/repo") is None
+
+    def test_rejects_subpath(self):
+        assert _GITHUB_URL_RE.match("https://github.com/owner/repo/tree/main") is None
+
+    def test_rejects_no_repo(self):
+        assert _GITHUB_URL_RE.match("https://github.com/justowner") is None
+
+
+# -- AnalyzeRepoRequest validation --------------------------------------------
+
+class TestAnalyzeRepoRequest:
+    def test_valid_url(self):
+        req = AnalyzeRepoRequest(github_url="https://github.com/owner/repo")
+        assert req.github_url == "https://github.com/owner/repo"
+
+    def test_strips_whitespace_and_slash(self):
+        req = AnalyzeRepoRequest(github_url="  https://github.com/owner/repo/  ")
+        assert req.github_url == "https://github.com/owner/repo"
+
+    def test_rejects_empty(self):
+        with pytest.raises(Exception):
+            AnalyzeRepoRequest(github_url="")
+
+    def test_rejects_non_github(self):
+        with pytest.raises(Exception):
+            AnalyzeRepoRequest(github_url="https://gitlab.com/owner/repo")
+
+
+# -- IndexConfig validation (from PR #266) ------------------------------------
+
+class TestIndexConfig:
+    def test_valid_paths(self):
+        cfg = IndexConfig(include_paths=["packages/effect", "packages/schema"])
+        assert cfg.include_paths == ["packages/effect", "packages/schema"]
+
+    def test_normalizes_slashes(self):
+        cfg = IndexConfig(include_paths=["/packages/effect/", " src "])
+        assert cfg.include_paths == ["packages/effect", "src"]
+
+    def test_normalizes_backslashes(self):
+        cfg = IndexConfig(include_paths=["packages\\effect"])
+        assert cfg.include_paths == ["packages/effect"]
+
+    def test_rejects_empty_string(self):
+        with pytest.raises(Exception):
+            IndexConfig(include_paths=["packages/effect", "  "])
+
+    def test_rejects_path_traversal(self):
+        with pytest.raises(Exception):
+            IndexConfig(include_paths=["../etc/passwd"])
+
+    def test_rejects_nested_traversal(self):
+        with pytest.raises(Exception):
+            IndexConfig(include_paths=["packages/../../etc"])
+
+    def test_rejects_non_string(self):
+        with pytest.raises(Exception):
+            IndexConfig(include_paths=[123])
+
+    def test_none_is_valid(self):
+        cfg = IndexConfig()
+        assert cfg.include_paths is None
+
+
+# -- _fetch_directory_tree grouping logic -------------------------------------
+
+# Build a fake GitHub tree response for testing grouping
+def _make_tree(paths: list[str]) -> dict:
+    """Build a mock GitHub Tree API response from file paths."""
+    return {
+        "truncated": False,
+        "tree": [{"path": p, "type": "blob"} for p in paths],
+    }
+
+
+class TestFetchDirectoryTree:
+    """Test directory grouping logic with mocked GitHub API."""
+
+    @pytest.mark.asyncio
+    async def test_flat_repo_groups_by_top_dir(self):
+        tree = _make_tree([
+            "src/main.py",
+            "src/utils.py",
+            "tests/test_main.py",
+            "README.md",
+        ])
+        with patch("routes.repos.httpx.AsyncClient") as mock_client:
+            mock_resp = MagicMock()
+            mock_resp.status_code = 200
+            mock_resp.json.return_value = tree
+            mock_client.return_value.__aenter__ = AsyncMock(return_value=MagicMock(
+                get=AsyncMock(return_value=mock_resp)
+            ))
+
+            result = await _fetch_directory_tree("owner", "repo", "main")
+
+        dir_names = [d["name"] for d in result["directories"]]
+        assert "src" in dir_names
+        assert result["total_files"] == 3  # README.md has no code ext
+
+    @pytest.mark.asyncio
+    async def test_monorepo_groups_at_package_level(self):
+        tree = _make_tree([
+            "packages/core/src/index.ts",
+            "packages/core/src/utils.ts",
+            "packages/cli/src/main.ts",
+            "scripts/build.ts",
+        ])
+        with patch("routes.repos.httpx.AsyncClient") as mock_client:
+            mock_resp = MagicMock()
+            mock_resp.status_code = 200
+            mock_resp.json.return_value = tree
+            mock_client.return_value.__aenter__ = AsyncMock(return_value=MagicMock(
+                get=AsyncMock(return_value=mock_resp)
+            ))
+
+            result = await _fetch_directory_tree("owner", "repo", "main")
+
+        dir_names = [d["name"] for d in result["directories"]]
+        # Should group at packages/core level, not just packages
+        assert "packages/core" in dir_names
+        assert "packages/cli" in dir_names
+        assert "scripts" in dir_names
+
+    @pytest.mark.asyncio
+    async def test_skips_node_modules(self):
+        tree = _make_tree([
+            "src/index.ts",
+            "node_modules/lodash/index.js",
+        ])
+        with patch("routes.repos.httpx.AsyncClient") as mock_client:
+            mock_resp = MagicMock()
+            mock_resp.status_code = 200
+            mock_resp.json.return_value = tree
+            mock_client.return_value.__aenter__ = AsyncMock(return_value=MagicMock(
+                get=AsyncMock(return_value=mock_resp)
+            ))
+
+            result = await _fetch_directory_tree("owner", "repo", "main")
+
+        assert result["total_files"] == 1
+
+    @pytest.mark.asyncio
+    async def test_large_repo_suggestion(self):
+        # 600 TypeScript files across 15 packages
+        paths = [f"packages/pkg{i}/src/file{j}.ts" for i in range(15) for j in range(40)]
+        tree = _make_tree(paths)
+
+        with patch("routes.repos.httpx.AsyncClient") as mock_client:
+            mock_resp = MagicMock()
+            mock_resp.status_code = 200
+            mock_resp.json.return_value = tree
+            mock_client.return_value.__aenter__ = AsyncMock(return_value=MagicMock(
+                get=AsyncMock(return_value=mock_resp)
+            ))
+
+            result = await _fetch_directory_tree("owner", "repo", "main")
+
+        assert result["suggestion"] == "large_repo"
+        assert result["total_files"] == 600
+
+    @pytest.mark.asyncio
+    async def test_small_repo_no_suggestion(self):
+        tree = _make_tree(["src/main.py", "src/utils.py"])
+
+        with patch("routes.repos.httpx.AsyncClient") as mock_client:
+            mock_resp = MagicMock()
+            mock_resp.status_code = 200
+            mock_resp.json.return_value = tree
+            mock_client.return_value.__aenter__ = AsyncMock(return_value=MagicMock(
+                get=AsyncMock(return_value=mock_resp)
+            ))
+
+            result = await _fetch_directory_tree("owner", "repo", "main")
+
+        assert result["suggestion"] is None