1 files changed, 117 insertions, 0 deletions
diff --git a/src/internal/fuzz/mutator_test.go b/src/internal/fuzz/mutator_test.go
new file mode 100644
index 0000000..cea7e2e
--- /dev/null
+++ b/src/internal/fuzz/mutator_test.go
@@ -0,0 +1,117 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuzz
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"strconv"
+	"testing"
+)
+
+func BenchmarkMutatorBytes(b *testing.B) {
+	origEnv := os.Getenv("GODEBUG")
+	defer func() { os.Setenv("GODEBUG", origEnv) }()
+	os.Setenv("GODEBUG", fmt.Sprintf("%s,fuzzseed=123", origEnv))
+	m := newMutator()
+
+	for _, size := range []int{
+		1,
+		10,
+		100,
+		1000,
+		10000,
+		100000,
+	} {
+		b.Run(strconv.Itoa(size), func(b *testing.B) {
+			buf := make([]byte, size)
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				// resize buffer to the correct shape and reset the PCG
+				buf = buf[0:size]
+				m.r = newPcgRand()
+				m.mutate([]any{buf}, workerSharedMemSize)
+			}
+		})
+	}
+}
+
+func BenchmarkMutatorString(b *testing.B) {
+	origEnv := os.Getenv("GODEBUG")
+	defer func() { os.Setenv("GODEBUG", origEnv) }()
+	os.Setenv("GODEBUG", fmt.Sprintf("%s,fuzzseed=123", origEnv))
+	m := newMutator()
+
+	for _, size := range []int{
+		1,
+		10,
+		100,
+		1000,
+		10000,
+		100000,
+	} {
+		b.Run(strconv.Itoa(size), func(b *testing.B) {
+			buf := make([]byte, size)
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				// resize buffer to the correct shape and reset the PCG
+				buf = buf[0:size]
+				m.r = newPcgRand()
+				m.mutate([]any{string(buf)}, workerSharedMemSize)
+			}
+		})
+	}
+}
+
+func BenchmarkMutatorAllBasicTypes(b *testing.B) {
+	origEnv := os.Getenv("GODEBUG")
+	defer func() { os.Setenv("GODEBUG", origEnv) }()
+	os.Setenv("GODEBUG", fmt.Sprintf("%s,fuzzseed=123", origEnv))
+	m := newMutator()
+
+	types := []any{
+		[]byte(""),
+		string(""),
+		false,
+		float32(0),
+		float64(0),
+		int(0),
+		int8(0),
+		int16(0),
+		int32(0),
+		int64(0),
+		uint8(0),
+		uint16(0),
+		uint32(0),
+		uint64(0),
+	}
+
+	for _, t := range types {
+		b.Run(fmt.Sprintf("%T", t), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				m.r = newPcgRand()
+				m.mutate([]any{t}, workerSharedMemSize)
+			}
+		})
+	}
+}
+
+func TestStringImmutability(t *testing.T) {
+	v := []any{"hello"}
+	m := newMutator()
+	m.mutate(v, 1024)
+	original := v[0].(string)
+	originalCopy := make([]byte, len(original))
+	copy(originalCopy, []byte(original))
+	for i := 0; i < 25; i++ {
+		m.mutate(v, 1024)
+	}
+	if !bytes.Equal([]byte(original), originalCopy) {
+		t.Fatalf("string was mutated: got %x, want %x", []byte(original), originalCopy)
+	}
+}