fuzz: add more fuzz tests

client.go

@@ -7,6 +7,7 @@
 	"io"
 	"os"
 	"runtime/debug"
+	"testing"
 )
 
 // ErrNotSupported is the error returned when the muxer doesn't support
@@ -35,12 +36,14 @@
 // on this ReadWriteCloser. It returns an error if, for example,
 // the muxer does not know how to handle this protocol.
 func SelectProtoOrFail[T StringLike](proto T, rwc io.ReadWriteCloser) (err error) {
-	defer func() {
-		if rerr := recover(); rerr != nil {
-			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
-			err = fmt.Errorf("panic selecting protocol: %s", rerr)
-		}
-	}()
+	if !testing.Testing() {
+		defer func() {
+			if rerr := recover(); rerr != nil {
+				fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+				err = fmt.Errorf("panic selecting protocol: %s", rerr)
+			}
+		}()
+	}
 
 	errCh := make(chan error, 1)
 	go func() {
@@ -70,12 +73,14 @@
 // SelectOneOf will perform handshakes with the protocols on the given slice
 // until it finds one which is supported by the muxer.
 func SelectOneOf[T StringLike](protos []T, rwc io.ReadWriteCloser) (proto T, err error) {
-	defer func() {
-		if rerr := recover(); rerr != nil {
-			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
-			err = fmt.Errorf("panic selecting one of protocols: %s", rerr)
-		}
-	}()
+	if !testing.Testing() {
+		defer func() {
+			if rerr := recover(); rerr != nil {
+				fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+				err = fmt.Errorf("panic selecting one of protocols: %s", rerr)
+			}
+		}()
+	}
 
 	if len(protos) == 0 {
 		return "", ErrNoProtocols

multistream.go

@@ -11,6 +11,7 @@
 	"os"
 	"runtime/debug"
 	"sync"
+	"testing"
 
 	"github.com/multiformats/go-varint"
 )
@@ -192,12 +193,14 @@
 // Negotiate performs protocol selection and returns the protocol name and
 // the matching handler function for it (or an error).
 func (msm *MultistreamMuxer[T]) Negotiate(rwc io.ReadWriteCloser) (proto T, handler HandlerFunc[T], err error) {
-	defer func() {
-		if rerr := recover(); rerr != nil {
-			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
-			err = fmt.Errorf("panic in multistream negotiation: %s", rerr)
-		}
-	}()
+	if !testing.Testing() {
+		defer func() {
+			if rerr := recover(); rerr != nil {
+				fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+				err = fmt.Errorf("panic in multistream negotiation: %s", rerr)
+			}
+		}()
+	}
 
 	// Send the multistream protocol ID
 	// Ignore the error here.  We want the handshake to finish, even if the

multistream_test.go

@@ -7,6 +7,7 @@
 	"fmt"
 	"io"
 	"net"
+	"slices"
 	"sort"
 	"strings"
 	"testing"
@@ -802,7 +803,7 @@
 }
 
 type rwc struct {
-	*strings.Reader
+	strings.Reader
 }
 
 func (*rwc) Write(b []byte) (int, error) {
@@ -813,21 +814,68 @@
 	return nil
 }
 
-func FuzzMultistream(f *testing.F) {
-	f.Add("/multistream/1.0.0")
-	f.Add(ProtocolID)
+func FuzzHandler(f *testing.F) {
+	f.Add("/noise", "/tls", "", "\x13/multistream/1.0.0\n\a/noise\n")
 
-	f.Fuzz(func(t *testing.T, b string) {
-		readStream := strings.NewReader(b)
-		input := &rwc{readStream}
+	f.Fuzz(func(t *testing.T, p1, p2, p3, b string) {
+		input := &rwc{*strings.NewReader(b)}
 
 		mux := NewMultistreamMuxer[string]()
-		mux.AddHandler("/a", nil)
-		mux.AddHandler("/b", nil)
+		h := func(protocol string, rwc io.ReadWriteCloser) error {
+			defer rwc.Close()
+			_, err := io.Copy(io.Discard, rwc)
+			return err
+		}
+		if p1 != "" {
+			mux.AddHandler(p1, h)
+		}
+		if p2 != "" {
+			mux.AddHandler(p2, h)
+		}
+		if p3 != "" {
+			mux.AddHandler(p3, h)
+		}
 		_ = mux.Handle(input)
 	})
 }
 
+func FuzzSelectOneOf(f *testing.F) {
+	f.Add("/noise", "/tls", "", "\x13/multistream/1.0.0\n\a/noise\n")
+
+	f.Fuzz(func(t *testing.T, p1, p2, p3, response string) {
+		protos := make([]string, 0, 3)
+		if p1 != "" {
+			protos = append(protos, p1)
+		}
+		if p2 != "" {
+			protos = append(protos, p2)
+		}
+		if p3 != "" {
+			protos = append(protos, p3)
+		}
+
+		r := &rwc{*strings.NewReader(response)}
+
+		p, err := SelectOneOf(protos, r)
+		if err != nil {
+			return
+		}
+		if !slices.Contains(protos, p) {
+			t.Fatal("matched proto which wasn't proposed")
+		}
+	})
+}
+
+func FuzzSelectOrFail(f *testing.F) {
+	f.Add("/noise", "\x13/multistream/1.0.0\n\a/noise\n")
+
+	f.Fuzz(func(t *testing.T, proto, response string) {
+		r := &rwc{*strings.NewReader(response)}
+
+		_ = SelectProtoOrFail(proto, r)
+	})
+}
+
 func TestComparableErrors(t *testing.T) {
 	var err1 error = ErrNotSupported[string]{[]string{"/a"}}
 	if !errors.Is(err1, ErrNotSupported[string]{}) {