test: add dcc sign bytes test (#71)

* test: add dcc sign bytes test

* chore: rename byt to buf as suggested by @rahulghangas

go.mod

@@ -14,7 +14,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/spf13/cast v1.5.0 // indirect
 	github.com/spf13/cobra v1.6.1
-	github.com/stretchr/testify v1.8.1 // indirect
+	github.com/stretchr/testify v1.8.1
 	github.com/tendermint/tm-db v0.6.7 // indirect
 	golang.org/x/crypto v0.2.0 // indirect
 	golang.org/x/net v0.2.0 // indirect

types/data_commitment_confirm_test.go

@@ -0,0 +1,62 @@
+package types_test
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"math/big"
+	"strconv"
+	"testing"
+
+	celestiatypes "github.com/celestiaorg/celestia-app/x/qgb/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/stretchr/testify/require"
+
+	"github.com/celestiaorg/orchestrator-relayer/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDataCommitmentTupleRootSignBytes(t *testing.T) {
+	nonce := int64(1)
+	commitment := bytes.Repeat([]byte{2}, 32)
+
+	hexRepresentation := strconv.FormatInt(nonce, 16)
+	// Make sure hex representation has even length
+	if len(hexRepresentation)%2 == 1 {
+		hexRepresentation = "0" + hexRepresentation
+	}
+	hexBytes, err := hex.DecodeString(hexRepresentation)
+	require.NoError(t, err)
+	paddedNonce, err := padBytes(hexBytes, 32)
+	require.NoError(t, err)
+
+	expectedHash := crypto.Keccak256Hash(append(
+		celestiatypes.DcDomainSeparator[:],
+		append(
+			paddedNonce,
+			commitment...,
+		)...,
+	))
+
+	result := types.DataCommitmentTupleRootSignBytes(big.NewInt(nonce), commitment)
+
+	assert.Equal(t, expectedHash, result)
+}
+
+// padBytes Pad bytes to a given length
+func padBytes(buf []byte, length int) ([]byte, error) {
+	l := len(buf)
+	if l > length {
+		return nil, fmt.Errorf(
+			"cannot pad bytes because length of bytes array: %d is greater than given length: %d",
+			l,
+			length,
+		)
+	}
+	if l == length {
+		return buf, nil
+	}
+	tmp := make([]byte, length)
+	copy(tmp[length-l:], buf)
+	return tmp, nil
+}