Add Inner Ring code

pkg/core/netmap/epoch/math_test.go

@@ -0,0 +1,28 @@
+package epoch
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEpochMath(t *testing.T) {
+	items := []struct {
+		mathFn func(Epoch, Epoch) Epoch
+
+		a, b, c uint64
+	}{
+		{
+			mathFn: Sum, a: 1, b: 2, c: 3},
+	}
+
+	for _, item := range items {
+		require.Equal(t,
+			item.mathFn(
+				FromUint64(item.a),
+				FromUint64(item.b),
+			),
+			FromUint64(item.c),
+		)
+	}
+}