[test] Add tests for guard.wasmAlloc, wasmDealloc, tryCallWasmFunction allocator path, and decodeWasmCallResult

[github-actions]

Test Coverage Improvement: wasm_parse.go (internal/guard)

Function Analyzed

• Package: internal/guard
• Functions: tryCallWasmFunction, wasmAlloc, wasmDealloc, decodeWasmCallResult, parsePathLabeledResponse
• Previous Coverage: 70.6%
• New Coverage: 74.2%
• Complexity: High (WASM runtime integration, allocator path, error handling)

Why These Functions?

tryCallWasmFunction was at 57.1% coverage — the allocator path (lines 198-220) was completely untested because no existing test WASM binary exported both alloc and dealloc functions. wasmAlloc and wasmDealloc were at 0% for the same reason.

Tests Added

• ✅ tryCallWasmFunction allocator path via WASM with alloc/dealloc exports
• ✅ wasmAlloc error: null pointer returned by alloc (returns 0)
• ✅ wasmAlloc error: alloc returns void (no result)
• ✅ wasmDealloc: nil function is no-op
• ✅ wasmDealloc: zero pointer is no-op
• ✅ wasmDealloc: zero size is no-op
• ✅ wasmDealloc: valid call (no-op in test WASM)
• ✅ decodeWasmCallResult: resultLen == 0 branch (empty byte slice)
• ✅ decodeWasmCallResult: resultLen < 0 but not -2 (negative error code)
• ✅ parsePathLabeledResponse: NewPathLabeledData error (invalid items_path)
• ✅ wasmMemorySize: nil memory → (0, false)

Four hand-assembled WASM binaries are included as []byte literals:

• allocGuardWasm: alloc returns 256, label_agent returns 0 (empty)
• allocReturnsZeroWasm: alloc returns 0 (null pointer error path)
• allocReturnsVoidWasm: alloc is void (no-result error path)
• labelReturnsNeg1Wasm: label_agent returns -1 (negative error code path)

Coverage Report

Before: 70.6% (internal/guard)
After:  74.2% (internal/guard)
Improvement: +3.6%

Function-level improvements:
  parsePathLabeledResponse:   84.6% → 100.0%
  tryCallWasmFunction:        57.1% →  83.3%
  decodeWasmCallResult:       66.7% →  72.2%
  wasmMemorySize:             85.7% → 100.0%
  wasmAlloc:                   0.0% →  90.0%
  wasmDealloc:                 0.0% →  75.0%

Test Execution

All 11 new tests pass:

--- PASS: TestParsePathLabeledResponse_NewPathLabeledDataError (0.00s)
--- PASS: TestTryCallWasmFunction_AllocatorPath (0.00s)
--- PASS: TestDecodeWasmCallResult_ResultLenZero (0.00s)
--- PASS: TestDecodeWasmCallResult_NegativeErrorCode (0.00s)
--- PASS: TestWasmAlloc_NullPointerReturned (0.00s)
--- PASS: TestWasmAlloc_NoResultReturned (0.00s)
--- PASS: TestWasmDealloc_NilFunctionIsNoOp (0.00s)
--- PASS: TestWasmDealloc_ZeroPtrIsNoOp (0.00s)
--- PASS: TestWasmDealloc_ZeroSizeIsNoOp (0.00s)
--- PASS: TestWasmDealloc_ValidCall (0.00s)
--- PASS: TestWasmMemorySize_NilMemory (0.00s)
PASS
ok  github.com/github/gh-aw-mcpg/internal/guard   0.013s

---

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

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Generated by Test Coverage Improver · sonnet46 19.6M · ◷

[Copilot]

Pull request overview

Adds targeted unit tests in internal/guard to improve coverage of wasm_parse.go, especially the previously-untested allocator (alloc/dealloc) path and several error/edge branches in WASM call decoding and response parsing.

Changes:

• Introduces hand-assembled WASM fixtures to exercise tryCallWasmFunction’s allocator path and related wasmAlloc/wasmDealloc branches.
• Adds tests for decodeWasmCallResult edge cases (0-length result and negative error codes) and wasmMemorySize(nil) behavior.
• Adds a test covering parsePathLabeledResponse error propagation when difc.NewPathLabeledData fails due to an invalid items_path.

Show a summary per file

File	Description
internal/guard/wasm_parse_coverage_test.go	Adds new WASM-backed coverage tests for allocator path and decode/parse edge cases in wasm_parse.go.

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• Files reviewed: 1/1 changed files
• Comments generated: 0