Fuzz wire package with recorded data (#1168)

Closes #1140.

internal/wire/records_test.go

@@ -0,0 +1,96 @@
+// Copyright 2021 FerretDB Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package wire
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+// loadRecords gets recursively all .bin files from the recordsPath directory,
+// parses their content to wire Msgs and returns them as an array of testCase
+// structs with headerB and bodyB fields set.
+// If no records are found, it returns nil and no error.
+func loadRecords(recordsPath string) ([]testCase, error) {
+	// Load recursively every file path with ".bin" extension from recordsPath directory
+	var recordFiles []string
+
+	err := filepath.WalkDir(recordsPath, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if filepath.Ext(entry.Name()) == ".bin" {
+			recordFiles = append(recordFiles, path)
+		}
+
+		return nil
+	})
+
+	switch {
+	case os.IsNotExist(err):
+		return nil, nil
+	case err != nil:
+		return nil, err
+	}
+
+	var resMsgs []testCase
+
+	// Read every record file, parse their content to wire messages
+	// and store them in the testCase struct
+	for _, path := range recordFiles {
+		f, err := os.Open(path)
+		if err != nil {
+			return nil, err
+		}
+
+		defer f.Close()
+
+		r := bufio.NewReader(f)
+
+		for {
+			header, body, err := ReadMessage(r)
+
+			if errors.Is(err, io.EOF) {
+				break
+			}
+
+			if err != nil {
+				return nil, err
+			}
+
+			headBytes, err := header.MarshalBinary()
+			if err != nil {
+				return nil, err
+			}
+
+			bodyBytes, err := body.MarshalBinary()
+			if err != nil {
+				return nil, err
+			}
+
+			resMsgs = append(resMsgs, testCase{
+				headerB: headBytes,
+				bodyB:   bodyBytes,
+			})
+		}
+	}
+
+	return resMsgs, nil
+}

internal/wire/wire_test.go

@@ -18,6 +18,7 @@ import (
 	"bufio"
 	"bytes"
 	"errors"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -118,6 +119,15 @@ func fuzzMessages(f *testing.F, testCases []testCase) {
 		f.Add(tc.expectedB)
 	}
 
+	records, err := loadRecords(filepath.Join("..", "..", "records"))
+	require.NoError(f, err)
+
+	f.Logf("%d recorded messages were added to the seed corpus", len(records))
+
+	for _, rec := range records {
+		f.Add(rec.bodyB)
+	}
+
 	f.Fuzz(func(t *testing.T, b []byte) {
 		t.Parallel()