chore: add a non-random test to reserve sample

Author: acud

pkg/storer/sample_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/ethersphere/bee/v2/pkg/cac"
 	"github.com/ethersphere/bee/v2/pkg/postage"
 
 	postagetesting "github.com/ethersphere/bee/v2/pkg/postage/testing"
@@ -309,6 +310,63 @@ func assertValidSample(t *testing.T, sample storer.Sample, minRadius uint8, anch
 	}
 }
 
+// TestSampleVectorCAC is a deterministic test vector that verifies the chunk
+// address and transformed address produced by MakeSampleUsingChunks for a
+// single hardcoded CAC chunk and anchor. It guards against regressions in the
+// BMT hashing or sampling pipeline.
+func TestSampleVectorCAC(t *testing.T) {
+	t.Parallel()
+
+	// Chunk content: 4096 bytes with repeating pattern i%256.
+	chunkContent := make([]byte, swarm.ChunkSize)
+	for i := range chunkContent {
+		chunkContent[i] = byte(i % 256)
+	}
+
+	ch, err := cac.New(chunkContent)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Attach a hardcoded (but otherwise irrelevant) stamp so that
+	// MakeSampleUsingChunks can read ch.Stamp() without panicking.
+	batchID := make([]byte, 32)
+	for i := range batchID {
+		batchID[i] = byte(i + 1)
+	}
+	sig := make([]byte, 65)
+	for i := range sig {
+		sig[i] = byte(i + 1)
+	}
+	ch = ch.WithStamp(postage.NewStamp(batchID, make([]byte, 8), make([]byte, 8), sig))
+
+	// Anchor: exactly 32 bytes, constant across runs.
+	anchor := []byte("swarm-test-anchor-deterministic!")
+
+	sample, err := storer.MakeSampleUsingChunks([]swarm.Chunk{ch}, anchor)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(sample.Items) != 1 {
+		t.Fatalf("expected 1 sample item, got %d", len(sample.Items))
+	}
+
+	item := sample.Items[0]
+
+	const (
+		wantChunkAddr       = "902406053a7a2f3a17f16097e1d0b4b6a4abeae6b84968f5503ae621f9522e16"
+		wantTransformedAddr = "9dee91d1ed794460474ffc942996bd713176731db4581a3c6470fe9862905a60"
+	)
+
+	if got := item.ChunkAddress.String(); got != wantChunkAddr {
+		t.Errorf("chunk address mismatch:\n got:  %s\n want: %s", got, wantChunkAddr)
+	}
+	if got := item.TransformedAddress.String(); got != wantTransformedAddr {
+		t.Errorf("transformed address mismatch:\n got:  %s\n want: %s", got, wantTransformedAddr)
+	}
+}
+
 func assertSampleNoErrors(t *testing.T, sample storer.Sample) {
 	t.Helper()