feat(verify): save and replay fuzz corpora

Assisted-by: GLM 5.3 Flash

verify/corpus_test.go

@@ -0,0 +1,158 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package verify
+
+import (
+	"encoding/json"
+	"math/rand"
+	"os"
+	"runtime"
+	"strconv"
+	"testing"
+)
+
+func loadBasicKernel(t *testing.T) *Kernel {
+	t.Helper()
+	k, err := Load("../testdata/verify/basic_amd64.s")
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	t.Cleanup(k.Close)
+	return k
+}
+
+func TestReplayEntry(t *testing.T) {
+	k := loadBasicKernel(t)
+
+	e := CorpusEntry{Func: "add", Args: []CorpusArg{
+		{Kind: "int", Value: "2"},
+		{Kind: "int", Value: "3"},
+	}}
+	out, err := k.ReplayEntry("add", e)
+	if err != nil {
+		t.Fatalf("ReplayEntry: %v", err)
+	}
+	if got := int64(GetUint64(out, 16)); got != 5 {
+		t.Errorf("replay add(2, 3) = %d, want 5", got)
+	}
+}
+
+func TestCorpusRoundTrip(t *testing.T) {
+	k := loadBasicKernel(t)
+
+	e := CorpusEntry{Func: "add", Args: []CorpusArg{
+		{Kind: "int", Value: "20"},
+		{Kind: "int", Value: "22"},
+	}}
+	data, err := json.Marshal(e)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	var back CorpusEntry
+	if err := json.Unmarshal(data, &back); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	out, err := k.ReplayEntry("add", back)
+	if err != nil {
+		t.Fatalf("ReplayEntry: %v", err)
+	}
+	if got := int64(GetUint64(out, 16)); got != 42 {
+		t.Errorf("round-trip replay = %d, want 42", got)
+	}
+}
+
+// TestGenDualArgsEntryReplayable checks that the entry recorded alongside a
+// generated input replays to the same observable call.
+func TestGenDualArgsEntryReplayable(t *testing.T) {
+	k := loadBasicKernel(t)
+
+	sig, ok := parseFuncSig("// func add(a, b int) int")
+	if !ok {
+		t.Fatal("parseFuncSig failed")
+	}
+	_, _, bufs, entry := genDualArgs(rand.New(rand.NewSource(1)), sig, 24)
+	if len(entry.Args) != 2 || entry.Args[0].Kind != "int" {
+		t.Fatalf("unexpected entry: %+v", entry)
+	}
+	out, err := k.ReplayEntry("add", entry)
+	if err != nil {
+		t.Fatalf("ReplayEntry: %v", err)
+	}
+	want := int64(GetUint64(out, 16))
+	got := entryInt(t, entry.Args[0]) + entryInt(t, entry.Args[1])
+	if got != want {
+		t.Errorf("replayed sum = %d, want %d", want, got)
+	}
+	runtime.KeepAlive(bufs)
+}
+
+func entryInt(t *testing.T, a CorpusArg) int64 {
+	t.Helper()
+	v, err := strconv.ParseUint(a.Value, 10, 64)
+	if err != nil {
+		t.Fatalf("entry value %q: %v", a.Value, err)
+	}
+	return int64(v)
+}
+
+// TestFuzzHookSavesFailures fuzzes add against the go-tool-asm build of a
+// sub kernel with the same signature, so every iteration mismatches (safely:
+// both kernels read only their own arguments) and the hook must record
+// replayable entries.
+func TestFuzzHookSavesFailures(t *testing.T) {
+	src := `#include "textflag.h"
+
+// func add(a, b int) int
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVQ a+0(FP), AX
+	ADDQ b+8(FP), AX
+	MOVQ AX, ret+16(FP)
+	RET
+
+// func sub(a, b int) int
+TEXT ·sub(SB), NOSPLIT, $0-24
+	MOVQ a+0(FP), AX
+	SUBQ b+8(FP), AX
+	MOVQ AX, ret+16(FP)
+	RET
+`
+	dir := t.TempDir()
+	file := dir + "/addsub_test_amd64.s"
+	if err := os.WriteFile(file, []byte(src), 0o644); err != nil {
+		t.Fatalf("write kernel: %v", err)
+	}
+	k, err := Load(file)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	t.Cleanup(k.Close)
+
+	sig, ok := parseFuncSig("// func add(a, b int) int")
+	if !ok {
+		t.Fatal("parseFuncSig failed")
+	}
+	gt, err := GroundTruth(file)
+	if err != nil {
+		t.Skipf("go tool asm unavailable: %v", err)
+	}
+
+	var saved []CorpusEntry
+	res := k.FuzzFuncHook("add", sig, gt["sub"], 5, 42, func(e CorpusEntry) {
+		saved = append(saved, e)
+	})
+	if res.Mismatches == 0 {
+		t.Fatal("expected mismatches against the sub reference")
+	}
+	if len(saved) == 0 {
+		t.Fatal("hook saved no entries despite mismatches")
+	}
+	for _, e := range saved {
+		if e.Func != "add" || len(e.Args) != 2 {
+			t.Errorf("bad entry: %+v", e)
+		}
+		if _, err := k.ReplayEntry(e.Func, e); err != nil {
+			t.Errorf("saved entry does not replay: %v", err)
+		}
+	}
+}