Add multithreading test for ProofBuilder (#926)

Author: AlCutter

client/proofbuilder_test.go

@@ -0,0 +1,80 @@
+// Copyright 2026 Google LLC. All Rights Reserved.
+//
+// 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 client_test is for client tests which have deps which would otherwise cause an import cycle.
+package client_test
+
+import (
+	"fmt"
+	"math/rand/v2"
+	"testing"
+	"time"
+
+	"github.com/transparency-dev/tessera"
+	"github.com/transparency-dev/tessera/client"
+	"github.com/transparency-dev/tessera/testonly"
+	"golang.org/x/sync/errgroup"
+)
+
+func TestProofBuilderIsThreadsafe(t *testing.T) {
+	ctx := t.Context()
+
+	// First, create a test log large enough to have a bunch of tiles/entrybundles.
+	treeSize := uint64(2468)
+
+	l, done := testonly.NewTestLog(t, tessera.NewAppendOptions().WithBatching(1024, 100*time.Millisecond).WithCheckpointInterval(100*time.Millisecond))
+	defer func() {
+		_ = done(ctx)
+	}()
+
+	var f tessera.IndexFuture
+	t.Logf("Growing log to %d entries", treeSize)
+	for i := range treeSize {
+		f = l.Appender.Add(ctx, tessera.NewEntry(fmt.Appendf(nil, "Entry %d", i)))
+	}
+	t.Logf("Awaiting integration")
+	if _, _, err := tessera.NewPublicationAwaiter(ctx, l.LogReader.ReadCheckpoint, 100*time.Millisecond).Await(ctx, f); err != nil {
+		t.Fatalf("Failed while awaiting: %v", err)
+	}
+
+	// Create a single ProofBuilder which we'll use below, shared between a number of concurrent goroutines.
+	pb, err := client.NewProofBuilder(ctx, treeSize, l.LogReader.ReadTile)
+	if err != nil {
+		t.Fatalf("NewProofBuilder: %v", err)
+	}
+
+	// Finally, spin up a bunch of goroutines asking for consistency and inclusion proofs from the same single ProofBuilder instance.
+	t.Logf("Exercising proof builder")
+	concurrency := 512
+
+	var wg errgroup.Group
+	for range concurrency {
+		wg.Go(func() error {
+			leafIndex := uint64(1 + rand.IntN(int(treeSize-1)))
+			if _, err := pb.InclusionProof(ctx, leafIndex); err != nil {
+				return fmt.Errorf("failure calling InclusionProof(%d): %v", leafIndex, err)
+			}
+
+			smaller := uint64(1 + rand.IntN(int(treeSize-1)))
+			if _, err := pb.ConsistencyProof(ctx, smaller, treeSize); err != nil {
+				return fmt.Errorf("failure calling ConsistencyProof(%d, %d): %v", smaller, treeSize, err)
+			}
+			return nil
+		})
+	}
+
+	if err := wg.Wait(); err != nil {
+		t.Errorf("Concurrent request failed: %v", err)
+	}
+}