[test] Add tests for middleware.wrapToolHandler

[github-actions]

Test Coverage Improvement: wrapToolHandler

Function Analyzed

• Package: internal/middleware
• Function: wrapToolHandler
• Previous Coverage: 88.6%
• New Coverage: 94.3%
• Complexity: High (~260 lines, multiple branches, jq integration, fast-path optimization)

Why This Function?

wrapToolHandler is the core middleware that intercepts tool responses, applies jq filters, checks payload size thresholds, saves large payloads to disk, and generates jq schema metadata. It had several uncovered branches despite being a critical code path, making it the highest-priority candidate by combined complexity × (1 - coverage) score.

Tests Added

New file: internal/middleware/jqschema_wrap_coverage_test.go

Test	Lines Covered	Description
TestWrapToolHandler_FastPath_BypassedWithUnknownEnvKey	629–631	Fast-path guard: onlyKnownKeys = false when env map has a key that's not "content" or "isError". Uses a marshalCallRecorder helper to prove json.Marshal(data) was called (fast path skipped).
TestWrapToolHandler_FastPath_BypassedWithTwoKeysOneUnknown	629–631	Same guard with len(env) == 2 (max that enters the loop) — one known key, one unknown.
TestWrapToolHandler_NilDataAfterFilter	706–708	A "null" jq filter on structured data with empty result.Content causes tryApplyToolResponseFilter to return filteredData = nil. With threshold=0, the code enters schema generation and hits case nil, producing a PayloadMetadata response with payloadSchema: null.
TestWrapToolHandler_SchemaGenerationError_CanceledContext	724–726, 729–734	A pre-cancelled context causes gojq's iter.Next() to return a context-cancellation error before walk_schema runs. schemaErr != nil triggers the graceful fallback that returns the original result instead of metadata.

Coverage Report

Before: wrapToolHandler  88.6%   internal/middleware 92.1%
After:  wrapToolHandler  94.3%   internal/middleware 94.1%
Improvement: +5.7pp on function, +2.0pp on package

Test Execution

All tests pass:

--- PASS: TestWrapToolHandler_FastPath_BypassedWithUnknownEnvKey (0.00s)
--- PASS: TestWrapToolHandler_FastPath_BypassedWithTwoKeysOneUnknown (0.00s)
--- PASS: TestWrapToolHandler_NilDataAfterFilter (0.00s)
--- PASS: TestWrapToolHandler_SchemaGenerationError_CanceledContext (0.00s)
PASS
ok  github.com/github/gh-aw-mcpg/internal/middleware 0.022s coverage: 94.1%

---

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Generated by Test Coverage Improver · 3.5K AIC · ⊞ 28.8K · ◷

[Copilot]

Pull request overview

Adds targeted unit tests in internal/middleware to exercise previously uncovered branches in wrapToolHandler (large-payload jqschema middleware), primarily around the fast-path guard conditions and schema-generation behavior.

Changes:

• Added new tests to ensure the fast-path optimization is bypassed when the backing payload map contains unknown keys.
• Added a test to cover the case nil path in schema generation when a jq filter turns structured data into null.
• Added a test intended to cover the schema-generation error fallback behavior.

Show a summary per file

File	Description
internal/middleware/jqschema_wrap_coverage_test.go	New tests covering additional wrapToolHandler branches (fast-path guard, nil schema path, schema error fallback).

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• Files reviewed: 1/1 changed files
• Comments generated: 1