Add NoTestsExtractedError handling and unit test for screen_gh_candidate

Co-authored-by: Copilot <copilot@github.com>

Author: haoranpb

src/bcbench/collection/collect_gh.py

@@ -10,7 +10,7 @@
 from bcbench.collection.patch_utils import extract_file_paths_from_patch, find_project_paths_from_diff, separate_patches
 from bcbench.config import get_config
 from bcbench.dataset import BugFixEntry
-from bcbench.exceptions import CollectionError
+from bcbench.exceptions import CollectionError, NoTestsExtractedError
 from bcbench.logger import get_logger
 from bcbench.operations import extract_tests_from_patch
 
@@ -83,7 +83,9 @@ def fail(reason: str) -> ScreeningResult:
                 file_contents[file_path] = gh_client.get_file_content(file_path, commit_id)
             except Exception:
                 logger.debug("Could not fetch file content for %s", file_path)
-    if not extract_tests_from_patch(patch_test, file_contents):
+    try:
+        extract_tests_from_patch(patch_test, file_contents)
+    except NoTestsExtractedError:
         return fail("No testable functions found in test patch")
 
     return ScreeningResult(pr_number=pr_number, repo=repo, passed=True)

tests/test_collect_gh.py

@@ -5,6 +5,7 @@
 
 import pytest
 
+from bcbench.collection.collect_gh import screen_gh_candidate
 from bcbench.collection.gh_client import GHClient
 from bcbench.collection.patch_utils import extract_file_paths_from_patch, find_project_paths_from_diff, separate_patches
 from bcbench.exceptions import CollectionError
@@ -210,6 +211,38 @@ def test_get_file_content_success(self):
             assert "codeunit 12345" in result
 
 
+class TestScreenGHCandidate:
+    def test_returns_failed_result_when_test_patch_has_no_testable_functions(self):
+        diff = """diff --git a/App/Apps/W1/Foo/app/Foo.Codeunit.al b/App/Apps/W1/Foo/app/Foo.Codeunit.al
+--- a/App/Apps/W1/Foo/app/Foo.Codeunit.al
++++ b/App/Apps/W1/Foo/app/Foo.Codeunit.al
+@@ -1,3 +1,4 @@
++// Fix code
+ procedure Main()
+ begin
+ end;
+diff --git a/App/Apps/W1/Foo/test/FooTests.Codeunit.al b/App/Apps/W1/Foo/test/FooTests.Codeunit.al
+--- a/App/Apps/W1/Foo/test/FooTests.Codeunit.al
++++ b/App/Apps/W1/Foo/test/FooTests.Codeunit.al
+@@ -1,3 +1,4 @@
++// Not a test procedure
+ procedure Helper()
+ begin
+ end;
+"""
+
+        with patch("bcbench.collection.collect_gh.GHClient") as mock_client_class:
+            mock_client = mock_client_class.return_value
+            mock_client.get_pr_info.return_value = {"mergeCommit": {"oid": "abc123"}}
+            mock_client.get_pr_diff.return_value = diff
+            mock_client.get_file_content.return_value = 'codeunit 12345 "Foo Tests"'
+
+            result = screen_gh_candidate(12345)
+
+            assert not result.passed
+            assert result.reason == "No testable functions found in test patch"
+
+
 class TestExtractFilePathsFromPatch:
     def test_extracts_single_file_path(self):
         patch = """diff --git a/App/Code.al b/App/Code.al