diff --git a/pkg/innerring/indexer_test.go b/pkg/innerring/indexer_test.go
new file mode 100644
index 00000000..493ae92d
--- /dev/null
+++ b/pkg/innerring/indexer_test.go
@@ -0,0 +1,225 @@
+package innerring
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/atomic"
+)
+
+func TestIndexerReturnsIndexes(t *testing.T) {
+	t.Parallel()
+	commiteeKeys, err := keys.NewPublicKeysFromStrings([]string{
+		"03ff65b6ae79134a4dce9d0d39d3851e9bab4ee97abf86e81e1c5bbc50cd2826ae",
+		"022bb4041c50d607ff871dec7e4cd7778388e0ea6849d84ccbd9aa8f32e16a8131",
+	})
+	require.NoError(t, err, "convert string to commitee public keys failed")
+	cf := &testCommiteeFetcher{
+		keys: commiteeKeys,
+	}
+
+	irKeys, err := keys.NewPublicKeysFromStrings([]string{
+		"038c862959e56b43e20f79187c4fe9e0bc7c8c66c1603e6cf0ec7f87ab6b08dc35",
+		"02ac920cd7df0b61b289072e6b946e2da4e1a31b9ab1c621bb475e30fa4ab102c3",
+		"022bb4041c50d607ff871dec7e4cd7778388e0ea6849d84ccbd9aa8f32e16a8131",
+	})
+	require.NoError(t, err, "convert string to IR public keys failed")
+	irf := &testIRFetcher{
+		keys: irKeys,
+	}
+
+	t.Run("success", func(t *testing.T) {
+		t.Parallel()
+		key := irKeys[2]
+
+		indexer := newInnerRingIndexer(cf, irf, key, time.Second)
+
+		idx, err := indexer.AlphabetIndex()
+		require.NoError(t, err, "failed to get alphabet index")
+		require.Equal(t, int32(1), idx, "invalid alphabet index")
+
+		idx, err = indexer.InnerRingIndex()
+		require.NoError(t, err, "failed to get IR index")
+		require.Equal(t, int32(2), idx, "invalid IR index")
+
+		size, err := indexer.InnerRingSize()
+		require.NoError(t, err, "failed to get IR size")
+		require.Equal(t, int32(3), size, "invalid IR size")
+	})
+
+	t.Run("not found alphabet", func(t *testing.T) {
+		t.Parallel()
+		key := irKeys[0]
+
+		indexer := newInnerRingIndexer(cf, irf, key, time.Second)
+
+		idx, err := indexer.AlphabetIndex()
+		require.NoError(t, err, "failed to get alphabet index")
+		require.Equal(t, int32(-1), idx, "invalid alphabet index")
+
+		idx, err = indexer.InnerRingIndex()
+		require.NoError(t, err, "failed to get IR index")
+		require.Equal(t, int32(0), idx, "invalid IR index")
+	})
+
+	t.Run("not found IR", func(t *testing.T) {
+		t.Parallel()
+		key := commiteeKeys[0]
+
+		indexer := newInnerRingIndexer(cf, irf, key, time.Second)
+
+		idx, err := indexer.AlphabetIndex()
+		require.NoError(t, err, "failed to get alphabet index")
+		require.Equal(t, int32(0), idx, "invalid alphabet index")
+
+		idx, err = indexer.InnerRingIndex()
+		require.NoError(t, err, "failed to get IR index")
+		require.Equal(t, int32(-1), idx, "invalid IR index")
+	})
+}
+
+func TestIndexerCachesIndexes(t *testing.T) {
+	t.Parallel()
+	commiteeKeys, err := keys.NewPublicKeysFromStrings([]string{})
+	require.NoError(t, err, "convert string to commitee public keys failed")
+	cf := &testCommiteeFetcher{
+		keys: commiteeKeys,
+	}
+
+	irKeys, err := keys.NewPublicKeysFromStrings([]string{})
+	require.NoError(t, err, "convert string to IR public keys failed")
+	irf := &testIRFetcher{
+		keys: irKeys,
+	}
+
+	key, err := keys.NewPublicKeyFromString("022bb4041c50d607ff871dec7e4cd7778388e0ea6849d84ccbd9aa8f32e16a8131")
+	require.NoError(t, err, "convert string to public key failed")
+
+	indexer := newInnerRingIndexer(cf, irf, key, time.Second)
+
+	idx, err := indexer.AlphabetIndex()
+	require.NoError(t, err, "failed to get alphabet index")
+	require.Equal(t, int32(-1), idx, "invalid alphabet index")
+
+	idx, err = indexer.InnerRingIndex()
+	require.NoError(t, err, "failed to get IR index")
+	require.Equal(t, int32(-1), idx, "invalid IR index")
+
+	size, err := indexer.InnerRingSize()
+	require.NoError(t, err, "failed to get IR size")
+	require.Equal(t, int32(0), size, "invalid IR size")
+
+	require.Equal(t, int32(1), cf.calls.Load(), "invalid commitee calls count")
+	require.Equal(t, int32(1), irf.calls.Load(), "invalid IR calls count")
+
+	idx, err = indexer.AlphabetIndex()
+	require.NoError(t, err, "failed to get alphabet index")
+	require.Equal(t, int32(-1), idx, "invalid alphabet index")
+
+	idx, err = indexer.InnerRingIndex()
+	require.NoError(t, err, "failed to get IR index")
+	require.Equal(t, int32(-1), idx, "invalid IR index")
+
+	size, err = indexer.InnerRingSize()
+	require.NoError(t, err, "failed to get IR size")
+	require.Equal(t, int32(0), size, "invalid IR size")
+
+	require.Equal(t, int32(1), cf.calls.Load(), "invalid commitee calls count")
+	require.Equal(t, int32(1), irf.calls.Load(), "invalid IR calls count")
+
+	time.Sleep(2 * time.Second)
+
+	idx, err = indexer.AlphabetIndex()
+	require.NoError(t, err, "failed to get alphabet index")
+	require.Equal(t, int32(-1), idx, "invalid alphabet index")
+
+	idx, err = indexer.InnerRingIndex()
+	require.NoError(t, err, "failed to get IR index")
+	require.Equal(t, int32(-1), idx, "invalid IR index")
+
+	size, err = indexer.InnerRingSize()
+	require.NoError(t, err, "failed to get IR size")
+	require.Equal(t, int32(0), size, "invalid IR size")
+
+	require.Equal(t, int32(2), cf.calls.Load(), "invalid commitee calls count")
+	require.Equal(t, int32(2), irf.calls.Load(), "invalid IR calls count")
+}
+
+func TestIndexerThrowsErrors(t *testing.T) {
+	t.Parallel()
+	cf := &testCommiteeFetcher{
+		err: fmt.Errorf("test commitee error"),
+	}
+
+	irKeys, err := keys.NewPublicKeysFromStrings([]string{})
+	require.NoError(t, err, "convert string to IR public keys failed")
+	irf := &testIRFetcher{
+		keys: irKeys,
+	}
+
+	key, err := keys.NewPublicKeyFromString("022bb4041c50d607ff871dec7e4cd7778388e0ea6849d84ccbd9aa8f32e16a8131")
+	require.NoError(t, err, "convert string to public key failed")
+
+	indexer := newInnerRingIndexer(cf, irf, key, time.Second)
+
+	idx, err := indexer.AlphabetIndex()
+	require.ErrorContains(t, err, "test commitee error", "error from commitee not throwed")
+	require.Equal(t, int32(0), idx, "invalid alphabet index")
+
+	idx, err = indexer.InnerRingIndex()
+	require.ErrorContains(t, err, "test commitee error", "error from IR not throwed")
+	require.Equal(t, int32(0), idx, "invalid IR index")
+
+	size, err := indexer.InnerRingSize()
+	require.ErrorContains(t, err, "test commitee error", "error from IR not throwed")
+	require.Equal(t, int32(0), size, "invalid IR size")
+
+	commiteeKeys, err := keys.NewPublicKeysFromStrings([]string{})
+	require.NoError(t, err, "convert string to commitee public keys failed")
+	cf = &testCommiteeFetcher{
+		keys: commiteeKeys,
+	}
+
+	irf = &testIRFetcher{
+		err: fmt.Errorf("test IR error"),
+	}
+
+	indexer = newInnerRingIndexer(cf, irf, key, time.Second)
+
+	idx, err = indexer.AlphabetIndex()
+	require.ErrorContains(t, err, "test IR error", "error from commitee not throwed")
+	require.Equal(t, int32(0), idx, "invalid alphabet index")
+
+	idx, err = indexer.InnerRingIndex()
+	require.ErrorContains(t, err, "test IR error", "error from IR not throwed")
+	require.Equal(t, int32(0), idx, "invalid IR index")
+
+	size, err = indexer.InnerRingSize()
+	require.ErrorContains(t, err, "test IR error", "error from IR not throwed")
+	require.Equal(t, int32(0), size, "invalid IR size")
+}
+
+type testCommiteeFetcher struct {
+	keys  keys.PublicKeys
+	err   error
+	calls atomic.Int32
+}
+
+func (f *testCommiteeFetcher) Committee() (keys.PublicKeys, error) {
+	f.calls.Inc()
+	return f.keys, f.err
+}
+
+type testIRFetcher struct {
+	keys  keys.PublicKeys
+	err   error
+	calls atomic.Int32
+}
+
+func (f *testIRFetcher) InnerRingKeys() (keys.PublicKeys, error) {
+	f.calls.Inc()
+	return f.keys, f.err
+}