test: gate go-libraries integration tests behind -tags=integration

Assisted-by: GLM 5.2

asm/evex_test.go

@@ -4,13 +4,10 @@
 package asm
 
 import (
-	"os"
 	"strings"
 	"testing"
 
 	"golang.org/x/arch/x86/x86asm"
-
-	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
 )
 
 // TestEvexGroundTruth checks the EVEX (AVX-512) encodings byte for byte
@@ -649,71 +646,6 @@ func TestEvexErrors(t *testing.T) {
 	}
 }
 
-// TestAssembleGoFlacAVX512Kernel assembles the whole production AVX-512
-// kernel — all functions plus the file-global idx16 constant — and checks
-// that the static-symbol load resolves to the right bytes in the image.
-// Skipped when the sibling repository is not checked out.
-func TestAssembleGoFlacAVX512Kernel(t *testing.T) {
-	path := "../../go-libraries/go-flac/avx512_amd64.s"
-	if _, err := os.Stat(path); err != nil {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	src, err := os.ReadFile(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	f, errs := parser.Parse(path, string(src))
-	if len(errs) > 0 {
-		t.Fatalf("parse: %v", errs)
-	}
-	img, err := AssembleFile(f)
-	if err != nil {
-		t.Fatalf("AssembleFile: %v", err)
-	}
-	if len(img.Funcs) != 10 {
-		t.Errorf("functions = %d, want 10", len(img.Funcs))
-	}
-
-	// idx16 as the DATA directives define it: dwords 1..16.
-	idx := make([]byte, 0, 64)
-	for i := 1; i <= 16; i++ {
-		idx = append(idx, byte(i), 0, 0, 0)
-	}
-	image := img.Bytes()
-	base := img.Symbols["idx16"]
-	if base == 0 {
-		t.Fatal("idx16 not laid out")
-	}
-	if got := image[base : base+64]; hexCompact(got) != hexCompact(idx) {
-		t.Errorf("idx16 contents %x, want %x", got, idx)
-	}
-
-	// The VMOVDQU32 idx16(SB), Z13 load (62 71 7e 48 6f 2d + rel32) must
-	// resolve to idx16 within the image.
-	loads := 0
-	for _, fn := range img.Funcs {
-		code := img.Code[fn.Offset : fn.Offset+fn.Size]
-		pat := []byte{0x62, 0x71, 0x7e, 0x48, 0x6f, 0x2d}
-		for pos := 0; ; {
-			i := indexOf(code[pos:], pat)
-			if i < 0 {
-				break
-			}
-			i += pos
-			rel := int32(uint32(code[i+6]) | uint32(code[i+7])<<8 | uint32(code[i+8])<<16 | uint32(code[i+9])<<24)
-			target := fn.Offset + i + 10 + int(rel)
-			if target != base {
-				t.Errorf("%s: idx16 load at +%d targets 0x%x, want 0x%x", fn.Name, i, target, base)
-			}
-			loads++
-			pos = i + 10
-		}
-	}
-	if loads != 1 {
-		t.Errorf("idx16 loads found = %d, want 1", loads)
-	}
-}
-
 // hexCompact renders bytes as a lowercase hex string without separators.
 func hexCompact(b []byte) string {
 	const hexdig = "0123456789abcdef"
@@ -724,17 +656,3 @@ func hexCompact(b []byte) string {
 	}
 	return string(out)
 }
-
-// indexOf returns the index of the first occurrence of pat in b, or -1.
-func indexOf(b, pat []byte) int {
-	for i := 0; i+len(pat) <= len(b); i++ {
-		j := 0
-		for j < len(pat) && b[i+j] == pat[j] {
-			j++
-		}
-		if j == len(pat) {
-			return i
-		}
-	}
-	return -1
-}

asm/integration_test.go

@@ -0,0 +1,159 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package asm integration tests against the production go-libraries kernels.
+// These are excluded from the default test run (go test ./...) so that the
+// coverage numbers are identical locally and in CI, where go-libraries is
+// not checked out.  Run them explicitly with:  go test -tags=integration ./asm/
+package asm
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"golang.org/x/arch/x86/x86asm"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestAssembleGoFlacAVX2Kernel assembles the whole production AVX2 kernel —
+// all functions plus the file-local mask24 constant — and checks that every
+// static-symbol load resolves to the right bytes in the image.
+func TestAssembleGoFlacAVX2Kernel(t *testing.T) {
+	path := "../../go-libraries/go-flac/avx2_amd64.s"
+	if _, err := os.Stat(path); err != nil {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	src, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, errs := parser.Parse(path, string(src))
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFile(f)
+	if err != nil {
+		t.Fatalf("AssembleFile: %v", err)
+	}
+	if len(img.Funcs) != 17 {
+		t.Errorf("functions = %d, want 17", len(img.Funcs))
+	}
+
+	// mask24 as the DATA directives define it.
+	mask := []byte{
+		0x00, 0x01, 0x02, 0x80, 0x03, 0x04, 0x05, 0x80,
+		0x06, 0x07, 0x08, 0x80, 0x09, 0x0a, 0x0b, 0x80,
+	}
+	image := img.Bytes()
+	if got := image[img.Symbols["mask24"] : img.Symbols["mask24"]+16]; !bytes.Equal(got, mask) {
+		t.Errorf("mask24 contents %x, want %x", got, mask)
+	}
+
+	// Every VMOVDQU mask24<>(SB), X15 (c5 7a 6f 3d + rel32, i.e. a VMOVDQU
+	// with a RIP-relative r/m) must land on the mask bytes within the image.
+	loads := 0
+	for _, fn := range img.Funcs {
+		code := img.Code[fn.Offset : fn.Offset+fn.Size]
+		for pc := 0; pc < len(code); {
+			inst, err := x86asm.Decode(code[pc:], 64)
+			if err != nil {
+				t.Fatalf("%s: decode at +%d: %v", fn.Name, pc, err)
+			}
+			// mod=00, rm=101 → RIP-relative.
+			if inst.Op == x86asm.VMOVDQU && inst.Len == 8 && code[pc+3]&0xC7 == 0x05 {
+				rel := int32(uint32(code[pc+4]) | uint32(code[pc+5])<<8 | uint32(code[pc+6])<<16 | uint32(code[pc+7])<<24)
+				target := fn.Offset + pc + 8 + int(rel)
+				if !bytes.Equal(image[target:target+16], mask) {
+					t.Errorf("%s: mask load at +%d lands on %x, want %x", fn.Name, pc, image[target:target+16], mask)
+				}
+				loads++
+			}
+			pc += inst.Len
+		}
+	}
+	if loads != 2 {
+		t.Errorf("mask loads found = %d, want 2", loads)
+	}
+}
+
+// TestAssembleGoFlacAVX512Kernel assembles the whole production AVX-512
+// kernel — all functions plus the file-global idx16 constant — and checks
+// that the static-symbol load resolves to the right bytes in the image.
+func TestAssembleGoFlacAVX512Kernel(t *testing.T) {
+	path := "../../go-libraries/go-flac/avx512_amd64.s"
+	if _, err := os.Stat(path); err != nil {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	src, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, errs := parser.Parse(path, string(src))
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFile(f)
+	if err != nil {
+		t.Fatalf("AssembleFile: %v", err)
+	}
+	if len(img.Funcs) != 10 {
+		t.Errorf("functions = %d, want 10", len(img.Funcs))
+	}
+
+	// idx16 as the DATA directives define it: dwords 1..16.
+	idx := make([]byte, 0, 64)
+	for i := 1; i <= 16; i++ {
+		idx = append(idx, byte(i), 0, 0, 0)
+	}
+	image := img.Bytes()
+	base := img.Symbols["idx16"]
+	if base == 0 {
+		t.Fatal("idx16 not laid out")
+	}
+	if got := image[base : base+64]; hexCompact(got) != hexCompact(idx) {
+		t.Errorf("idx16 contents %x, want %x", got, idx)
+	}
+
+	// The VMOVDQU32 idx16(SB), Z13 load (62 71 7e 48 6f 2d + rel32) must
+	// resolve to idx16 within the image.
+	loads := 0
+	for _, fn := range img.Funcs {
+		code := img.Code[fn.Offset : fn.Offset+fn.Size]
+		pat := []byte{0x62, 0x71, 0x7e, 0x48, 0x6f, 0x2d}
+		for pos := 0; ; {
+			i := indexOf(code[pos:], pat)
+			if i < 0 {
+				break
+			}
+			i += pos
+			rel := int32(uint32(code[i+6]) | uint32(code[i+7])<<8 | uint32(code[i+8])<<16 | uint32(code[i+9])<<24)
+			target := fn.Offset + i + 10 + int(rel)
+			if target != base {
+				t.Errorf("%s: idx16 load at +%d targets 0x%x, want 0x%x", fn.Name, i, target, base)
+			}
+			loads++
+			pos = i + 10
+		}
+	}
+	if loads != 1 {
+		t.Errorf("idx16 loads found = %d, want 1", loads)
+	}
+}
+
+// indexOf returns the index of the first occurrence of pat in b, or -1.
+func indexOf(b, pat []byte) int {
+	for i := 0; i+len(pat) <= len(b); i++ {
+		j := 0
+		for j < len(pat) && b[i+j] == pat[j] {
+			j++
+		}
+		if j == len(pat) {
+			return i
+		}
+	}
+	return -1
+}

asm/link_test.go

@@ -4,13 +4,9 @@
 package asm
 
 import (
-	"bytes"
-	"os"
 	"strings"
 	"testing"
 
-	"golang.org/x/arch/x86/x86asm"
-
 	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
 )
 
@@ -132,65 +128,3 @@ DATA x<>+0(SB)/4, $1
 		t.Errorf("single-function SB: error %v, want a file-level-assembly error", err)
 	}
 }
-
-// TestAssembleGoFlacAVX2Kernel assembles the whole production AVX2 kernel —
-// all functions plus the file-local mask24 constant — and checks that every
-// static-symbol load resolves to the right bytes in the image.  Skipped when
-// the sibling repository is not checked out.
-func TestAssembleGoFlacAVX2Kernel(t *testing.T) {
-	path := "../../go-libraries/go-flac/avx2_amd64.s"
-	if _, err := os.Stat(path); err != nil {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	src, err := os.ReadFile(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	f, errs := parser.Parse(path, string(src))
-	if len(errs) > 0 {
-		t.Fatalf("parse: %v", errs)
-	}
-	img, err := AssembleFile(f)
-	if err != nil {
-		t.Fatalf("AssembleFile: %v", err)
-	}
-	if len(img.Funcs) != 17 {
-		t.Errorf("functions = %d, want 17", len(img.Funcs))
-	}
-
-	// mask24 as the DATA directives define it.
-	mask := []byte{
-		0x00, 0x01, 0x02, 0x80, 0x03, 0x04, 0x05, 0x80,
-		0x06, 0x07, 0x08, 0x80, 0x09, 0x0a, 0x0b, 0x80,
-	}
-	image := img.Bytes()
-	if got := image[img.Symbols["mask24"] : img.Symbols["mask24"]+16]; !bytes.Equal(got, mask) {
-		t.Errorf("mask24 contents %x, want %x", got, mask)
-	}
-
-	// Every VMOVDQU mask24<>(SB), X15 (c5 7a 6f 3d + rel32, i.e. a VMOVDQU
-	// with a RIP-relative r/m) must land on the mask bytes within the image.
-	loads := 0
-	for _, fn := range img.Funcs {
-		code := img.Code[fn.Offset : fn.Offset+fn.Size]
-		for pc := 0; pc < len(code); {
-			inst, err := x86asm.Decode(code[pc:], 64)
-			if err != nil {
-				t.Fatalf("%s: decode at +%d: %v", fn.Name, pc, err)
-			}
-			// mod=00, rm=101 → RIP-relative.
-			if inst.Op == x86asm.VMOVDQU && inst.Len == 8 && code[pc+3]&0xC7 == 0x05 {
-				rel := int32(uint32(code[pc+4]) | uint32(code[pc+5])<<8 | uint32(code[pc+6])<<16 | uint32(code[pc+7])<<24)
-				target := fn.Offset + pc + 8 + int(rel)
-				if !bytes.Equal(image[target:target+16], mask) {
-					t.Errorf("%s: mask load at +%d lands on %x, want %x", fn.Name, pc, image[target:target+16], mask)
-				}
-				loads++
-			}
-			pc += inst.Len
-		}
-	}
-	if loads != 2 {
-		t.Errorf("mask loads found = %d, want 2", loads)
-	}
-}

format/format_test.go

@@ -5,7 +5,6 @@ package format
 
 import (
 	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 
@@ -172,11 +171,9 @@ func TestIdempotent(t *testing.T) {
 }
 
 // TestRoundTrip checks that formatting produces source that still parses
-// cleanly, on the fixture and on the real go-flac kernels when present.
+// cleanly on the in-repository fixture.
 func TestRoundTrip(t *testing.T) {
 	files := []string{"../testdata/sample_amd64.s"}
-	real, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	files = append(files, real...)
 	for _, path := range files {
 		src, err := os.ReadFile(path)
 		if err != nil {

format/integration_test.go

@@ -0,0 +1,40 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package format integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./format/
+package format
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestRoundTripRealGoLibraries checks that formatting the production kernels
+// still produces source that parses cleanly.
+func TestRoundTripRealGoLibraries(t *testing.T) {
+	real, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(real) == 0 {
+		t.Skip("go-libraries repository not present")
+	}
+	for _, path := range real {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		formatted := Source(path, string(src))
+		if _, errs := parser.Parse(path, formatted); len(errs) > 0 {
+			t.Errorf("formatted %s no longer parses: %v", path, errs)
+		}
+		if strings.TrimSpace(formatted) == "" {
+			t.Errorf("formatted %s is empty", path)
+		}
+	}
+}

lint/integration_test.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package lint integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./lint/
+package lint
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestRealGoLibrariesHasNoErrors asserts that the production go-flac kernels
+// lint free of errors.
+func TestRealGoLibrariesHasNoErrors(t *testing.T) {
+	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(matches) == 0 {
+		t.Skip("go-libraries repository not present")
+	}
+	for _, path := range matches {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		f, errs := parser.Parse(path, string(src))
+		if len(errs) > 0 {
+			t.Fatalf("parse %s: %v", path, errs)
+		}
+		a := arch.FromFilename(path)
+		diags := File(f, Config{Arch: a})
+		for _, d := range diags {
+			if d.Severity == Error {
+				t.Errorf("%s: %s %s: %s", filepath.Base(path), d.Pos, d.Code, d.Message)
+			}
+		}
+	}
+}

lint/lint_test.go

@@ -5,7 +5,6 @@ package lint
 
 import (
 	"os"
-	"path/filepath"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
@@ -234,29 +233,3 @@ TEXT ·f(SB), NOSPLIT, $0
 		t.Fatalf("label rules should be suppressed in macro files: %+v", diags)
 	}
 }
-
-// TestRealGoLibrariesHasNoErrors asserts that the production go-flac kernels
-// lint free of errors.  Skipped when the sibling repository is absent.
-func TestRealGoLibrariesHasNoErrors(t *testing.T) {
-	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	if len(matches) == 0 {
-		t.Skip("go-libraries repository not present")
-	}
-	for _, path := range matches {
-		src, err := os.ReadFile(path)
-		if err != nil {
-			t.Fatal(err)
-		}
-		f, errs := parser.Parse(path, string(src))
-		if len(errs) > 0 {
-			t.Fatalf("parse %s: %v", path, errs)
-		}
-		a := arch.FromFilename(path)
-		diags := File(f, Config{Arch: a})
-		for _, d := range diags {
-			if d.Severity == Error {
-				t.Errorf("%s: %s %s: %s", filepath.Base(path), d.Pos, d.Code, d.Message)
-			}
-		}
-	}
-}

parser/integration_test.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package parser integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./parser/
+package parser
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestParseRealGoLibraries parses every .s file in the sibling go-libraries
+// repository when it is checked out, asserting a clean, error-free parse.
+func TestParseRealGoLibraries(t *testing.T) {
+	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(matches) == 0 {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	for _, path := range matches {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatalf("read %s: %v", path, err)
+		}
+		file, errs := Parse(path, string(src))
+		if len(errs) > 0 {
+			t.Errorf("parse %s: %v", path, errs)
+			continue
+		}
+		if len(texts(file)) == 0 {
+			t.Errorf("parse %s: no TEXT functions found", path)
+		}
+		t.Logf("%s: %d decls, %d functions", filepath.Base(path), len(file.Decls), len(texts(file)))
+	}
+}

parser/parser_test.go

@@ -5,7 +5,6 @@ package parser
 
 import (
 	"os"
-	"path/filepath"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
@@ -254,28 +253,3 @@ func TestDataWidthAndStatic(t *testing.T) {
 		t.Errorf("mask24 DATA should be static, got %+v", datas[2].Name)
 	}
 }
-
-// TestParseRealGoLibraries parses every .s file in the sibling go-libraries
-// repository when it is checked out, asserting a clean, error-free parse.  It
-// is skipped when the repository is not present.
-func TestParseRealGoLibraries(t *testing.T) {
-	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	if len(matches) == 0 {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	for _, path := range matches {
-		src, err := os.ReadFile(path)
-		if err != nil {
-			t.Fatalf("read %s: %v", path, err)
-		}
-		file, errs := Parse(path, string(src))
-		if len(errs) > 0 {
-			t.Errorf("parse %s: %v", path, errs)
-			continue
-		}
-		if len(texts(file)) == 0 {
-			t.Errorf("parse %s: no TEXT functions found", path)
-		}
-		t.Logf("%s: %d decls, %d functions", filepath.Base(path), len(file.Decls), len(texts(file)))
-	}
-}

verify/fuzz_extra_test.go

@@ -50,3 +50,118 @@ func TestArrayLen(t *testing.T) {
 		}
 	}
 }
+
+func TestElemSizeFor(t *testing.T) {
+	tests := []struct {
+		typ  string
+		want int
+	}{
+		{"[]byte", 1}, {"[]uint8", 1}, {"[]int8", 1},
+		{"[]uint16", 2}, {"[]int16", 2},
+		{"[]uint32", 4}, {"[]int32", 4}, {"[]float32", 4},
+		{"[]uint64", 8}, {"[]int64", 8}, {"[]float64", 8},
+		{"[]unknown", 8},
+	}
+	for _, tt := range tests {
+		if got := elemSizeFor(tt.typ); got != tt.want {
+			t.Errorf("elemSizeFor(%q) = %d, want %d", tt.typ, got, tt.want)
+		}
+	}
+}
+
+func TestEqualBytes(t *testing.T) {
+	if !equalBytes([]byte{1, 2, 3}, []byte{1, 2, 3}) {
+		t.Error("expected equal")
+	}
+	if equalBytes([]byte{1, 2}, []byte{1, 2, 3}) {
+		t.Error("different length: expected not equal")
+	}
+	if equalBytes([]byte{1, 2, 3}, []byte{1, 2, 4}) {
+		t.Error("different content: expected not equal")
+	}
+}
+
+func TestParamsSize(t *testing.T) {
+	sig := funcSig{
+		name:    "test",
+		params:  []param{{name: "a", typ: "[]byte"}, {name: "b", typ: "int"}},
+		results: []param{{name: "n", typ: "int"}},
+	}
+	if got := paramsSize(sig); got != 32 {
+		t.Errorf("paramsSize = %d, want 32 (24 for slice + 8 for int)", got)
+	}
+}
+
+func TestBlockCount(t *testing.T) {
+	k := loadBasic(t)
+	n, err := k.BlockCount("sum")
+	if err != nil {
+		t.Fatalf("BlockCount(sum): %v", err)
+	}
+	if n < 2 {
+		t.Errorf("sum: expected at least 2 blocks, got %d", n)
+	}
+}
+
+func TestFillBuffer(t *testing.T) {
+	t.Run("zero", func(t *testing.T) {
+		// fillBuffer("zero") is a no-op — relies on make already zeroing.
+		buf := make([]byte, 16)
+		fillBuffer(buf, "zero")
+		for _, b := range buf {
+			if b != 0 {
+				t.Error("zero pattern: make should produce zeroed buffer")
+				break
+			}
+		}
+	})
+	t.Run("ones", func(t *testing.T) {
+		buf := make([]byte, 16)
+		fillBuffer(buf, "ones")
+		for _, b := range buf {
+			if b != 0xFF {
+				t.Error("ones pattern should fill with 0xFF")
+				break
+			}
+		}
+	})
+	t.Run("seq", func(t *testing.T) {
+		buf := make([]byte, 256)
+		fillBuffer(buf, "seq")
+		for i, b := range buf {
+			if b != byte(i) {
+				t.Errorf("seq[%d] = %d, want %d", i, b, i)
+				break
+			}
+		}
+	})
+	t.Run("hex", func(t *testing.T) {
+		buf := make([]byte, 6)
+		fillBuffer(buf, "deadbeef")
+		want := []byte{0xDE, 0xAD, 0xBE, 0xEF, 0xDE, 0xAD}
+		for i, b := range buf {
+			if b != want[i] {
+				t.Errorf("hex[%d] = %02x, want %02x", i, b, want[i])
+				break
+			}
+		}
+	})
+}
+
+func TestFuzzFuncChecked(t *testing.T) {
+	k := loadBasic(t)
+	sig := funcSig{
+		name:    "sum",
+		params:  []param{{name: "data", typ: "[]int64"}},
+		results: []param{{name: "r", typ: "int64"}},
+	}
+	result := k.FuzzFuncChecked("sum", sig, 10, 0)
+	if !result.OK() {
+		t.Errorf("FuzzFuncChecked(sum): %s", result)
+	}
+	// Test with non-existent function — should report failure.
+	result = k.FuzzFuncChecked("nope", sig, 10, 0)
+	if result.OK() {
+		t.Error("FuzzFuncChecked(nope): expected failure")
+	}
+}