[test] Add tests for config.validateAgainstCustomSchema

[github-actions]

Test Coverage Improvement: validateAgainstCustomSchema and validateCustomServerConfig

Function Analyzed

• Package: internal/config
• Functions: validateAgainstCustomSchema, validateCustomServerConfig
• File: internal/config/validation.go
• Complexity: High — 9+ branches, schema fetching, JSON parsing, compiler setup, AdditionalProperties merging, type assertion fallbacks

Why This Function?

validateAgainstCustomSchema (lines 202–314 in validation.go) is a complex function with multiple independent error paths, several of which had zero test coverage before this PR:

1. HTTP fetch failure — schema server returns non-200 status
2. Connection failure — schema URL is unreachable
3. Schema $id different from fetch URL — triggers the schemaID != schemaURL branch that registers the schema under both URLs before compilation
4. AdditionalProperties merging — custom fields stored in server.AdditionalProperties must be merged into the validation map

validateCustomServerConfig (lines 167–199) also had an untested branch:
5. Non-string schema value — when customSchemas[type] holds a non-string (e.g., int, bool, map), the type assertion fallback silently sets schemaURL = "" and skips validation

Tests Added

New file: internal/config/validate_against_custom_schema_test.go

Test	Branch covered
TestValidateAgainstCustomSchema_FetchFailure	fetchAndFixSchema error — HTTP 500
TestValidateAgainstCustomSchema_UnreachableURL	fetchAndFixSchema error — connection refused
TestValidateAgainstCustomSchema_SchemaWithDifferentID	schemaID != schemaURL happy path
TestValidateAgainstCustomSchema_SchemaWithDifferentID_MissingRequired	schemaID != schemaURL + validation failure
TestValidateAgainstCustomSchema_AdditionalPropertiesMerged	AdditionalProperties loop (lines 297–299)
TestValidateAgainstCustomSchema_AdditionalPropertiesMissingRequired	AdditionalProperties missing required field
TestValidateCustomServerConfig_NonStringSchemaValue	schemaValue.(string) type assertion fallback (4 sub-cases)
TestValidateCustomServerConfig_NilCustomSchemas	customSchemas == nil path directly
TestValidateCustomServerConfig_UnregisteredType	!exists path directly

Test Execution

Tests are structured as table-driven and sub-tests using httptest.NewServer mock servers (matching the pattern in custom_types_test.go) and use require/assert from testify.

---

Generated by Test Coverage Improver
Next run will target the next most complex under-tested function

AI generated by Test Coverage Improver

[Copilot]

Pull request overview

This PR adds comprehensive unit tests for two previously under-tested functions in the internal/config package: validateAgainstCustomSchema and validateCustomServerConfig. These functions handle custom server type validation against JSON schemas, with complex error paths and edge cases that were not fully exercised by the existing compliance tests (T-CFG-010 through T-CFG-014).

Changes:

• Added 9 new test cases covering HTTP fetch failures, unreachable URLs, schema $id handling, AdditionalProperties merging, and non-string schema value handling
• Tests use httptest mock servers and table-driven patterns consistent with existing test conventions
• All tests follow established patterns using testify/assert and testify/require

---

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