paymentsdb: introduce a harness interface

The design of the sql and kv db are a bit different. A harness
interface is introduced which allows us to unit most of the test
and keep the backend specific tests at a minimum.

payments/db/test_kvdb.go

@@ -3,14 +3,18 @@
 package paymentsdb
 
 import (
+	"bytes"
 	"testing"
 
+	"github.com/btcsuite/btcwallet/walletdb"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
 // NewTestDB is a helper function that creates an BBolt database for testing.
-func NewTestDB(t *testing.T, opts ...OptionModifier) DB {
+func NewTestDB(t *testing.T, opts ...OptionModifier) (DB, TestHarness) {
 	backend, backendCleanup, err := kvdb.GetTestBackend(
 		t.TempDir(), "paymentsDB",
 	)
@@ -21,7 +25,7 @@ func NewTestDB(t *testing.T, opts ...OptionModifier) DB {
 	paymentDB, err := NewKVStore(backend, opts...)
 	require.NoError(t, err)
 
-	return paymentDB
+	return paymentDB, &kvTestHarness{db: paymentDB}
 }
 
 // NewKVTestDB is a helper function that creates an BBolt database for testing
@@ -40,3 +44,68 @@ func NewKVTestDB(t *testing.T, opts ...OptionModifier) *KVStore {
 
 	return paymentDB
 }
+
+// kvTestHarness is the KV-specific test harness implementation.
+type kvTestHarness struct {
+	db *KVStore
+}
+
+// AssertPaymentIndex looks up the index for a payment in the db and checks
+// that its payment hash matches the expected hash passed in.
+func (h *kvTestHarness) AssertPaymentIndex(t *testing.T,
+	expectedHash lntypes.Hash) {
+
+	t.Helper()
+
+	// Lookup the payment so that we have its sequence number and check
+	// that it has correctly been indexed in the payment indexes bucket.
+	pmt, err := h.db.FetchPayment(expectedHash)
+	require.NoError(t, err)
+
+	hash, err := h.fetchPaymentIndexEntry(t, pmt.SequenceNum)
+	require.NoError(t, err)
+	assert.Equal(t, expectedHash, *hash)
+}
+
+// AssertNoIndex checks that an index for the sequence number provided does not
+// exist.
+func (h *kvTestHarness) AssertNoIndex(t *testing.T, seqNr uint64) {
+	t.Helper()
+
+	_, err := h.fetchPaymentIndexEntry(t, seqNr)
+	require.Equal(t, ErrNoSequenceNrIndex, err)
+}
+
+// fetchPaymentIndexEntry gets the payment hash for the sequence number
+// provided from the payment indexes bucket.
+func (h *kvTestHarness) fetchPaymentIndexEntry(t *testing.T,
+	sequenceNumber uint64) (*lntypes.Hash, error) {
+
+	t.Helper()
+
+	var hash lntypes.Hash
+
+	if err := kvdb.View(h.db.db, func(tx walletdb.ReadTx) error {
+		indexBucket := tx.ReadBucket(paymentsIndexBucket)
+		key := make([]byte, 8)
+		byteOrder.PutUint64(key, sequenceNumber)
+
+		indexValue := indexBucket.Get(key)
+		if indexValue == nil {
+			return ErrNoSequenceNrIndex
+		}
+
+		r := bytes.NewReader(indexValue)
+
+		var err error
+		hash, err = deserializePaymentIndex(r)
+
+		return err
+	}, func() {
+		hash = lntypes.Hash{}
+	}); err != nil {
+		return nil, err
+	}
+
+	return &hash, nil
+}