chore: Update .coderabbit.yaml configuration to add pre-merge checks (#9980)

* chore: Update .coderabbit.yaml configuration for review processes

- Added pre-merge checks for test coverage, quality, and file naming to enhance testing standards.

* chore: Refine .coderabbit.yaml review instructions for testing standards

- Updated test coverage checks to emphasize the inclusion of corresponding tests for new components and improved clarity on test quality evaluation.
- Adjusted modes for warnings and errors to enhance the review process, ensuring better adherence to testing best practices.
- Introduced a new check for excessive mock usage to promote better test design and reliability.

.coderabbit.yaml

@@ -1,14 +1,14 @@
 language: en-US
-tone_instructions: ''
+tone_instructions: ""
 early_access: true
 enable_free_tier: true
 reviews:
   profile: chill
   request_changes_workflow: false
   high_level_summary: true
-  high_level_summary_placeholder: '@coderabbitai summary'
+  high_level_summary_placeholder: "@coderabbitai summary"
   high_level_summary_in_walkthrough: false
-  auto_title_placeholder: '@coderabbitai'
+  auto_title_placeholder: "@coderabbitai"
   auto_title_instructions: Use conventional commits structure
   review_status: true
   commit_status: true
@@ -26,7 +26,7 @@ reviews:
   poem: false
   labeling_instructions: []
   path_filters:
-    - '!src/backend/base/langflow/initial_setup/starter_projects'
+    - "!src/backend/base/langflow/initial_setup/starter_projects"
   path_instructions: []
   abort_on_close: true
   disable_cache: false
@@ -42,6 +42,46 @@ reviews:
       enabled: true
     unit_tests:
       enabled: true
+  pre_merge_checks:
+    custom_checks:
+      - name: "Test Coverage for New Implementations"
+        instructions: |
+          Check if the PR includes new or updated test files that correspond to the code changes:
+          1. For new components or functionality, ensure corresponding tests are included in the PR
+          2. For bug fixes, verify that regression tests are included
+          3. For new features, ensure both unit and integration tests are present where appropriate
+          4. Check that test files follow the project's naming conventions (test_*.py for backend, *.test.ts for frontend)
+          5. Verify that tests actually test the new functionality, not just placeholder tests
+        mode: "error"
+      - name: "Test Quality and Coverage"
+        instructions: |
+          Evaluate the quality and comprehensiveness of tests for new implementations:
+          1. Tests should cover the main functionality being implemented
+          2. For async functions, ensure proper async testing patterns are used (pytest for backend)
+          3. Check that tests are not just smoke tests but actually validate behavior
+          4. Ensure tests follow the project's testing patterns (pytest for backend, Playwright for frontend)
+          5. For API endpoints, verify both success and error response testing
+        mode: "warning"
+      - name: "Test File Naming and Structure"
+        instructions: |
+          Verify that test files follow the correct patterns and structure:
+          1. Backend tests: test_*.py with proper pytest structure
+          2. Frontend tests: *.test.ts or *.test.tsx using Playwright
+          3. Integration tests should be clearly marked and in appropriate directories
+          4. Test files should have descriptive test function names that explain what is being tested
+          5. Tests should be organized logically with proper setup and teardown
+          6. Consider including edge cases and error conditions for comprehensive coverage
+          7. Verify tests cover both positive and negative scenarios where appropriate
+        mode: "warning"
+      - name: "Excessive Mock Usage Warning"
+        instructions: |
+          Review test files for excessive use of mocks that may indicate poor test design:
+          1. Check if tests have too many mock objects that obscure what's actually being tested
+          2. Warn when mocks are used instead of testing real behavior and interactions
+          3. Suggest using real objects or test doubles when mocks become excessive
+          4. Ensure mocks are used appropriately for external dependencies, not core logic
+          5. Recommend integration tests when unit tests become overly mocked
+        mode: "warning"
   tools:
     ast-grep:
       rule_dirs: []