Add light sync command

- Only syncs block headers (excludes block bodies, transactions, receipts, and logs)
- Modifies validation window to include the most recent block
- Isolates validation window to the variable defined in the cmd directory (blocks
  have a separate variable defined in the block_repository for determining when
  to set a block as final)

pkg/history/block_validator_test.go

@@ -0,0 +1,43 @@
+package history_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/vulcanize/vulcanizedb/pkg/core"
+	"github.com/vulcanize/vulcanizedb/pkg/datastore/inmemory"
+	"github.com/vulcanize/vulcanizedb/pkg/fakes"
+	"github.com/vulcanize/vulcanizedb/pkg/history"
+)
+
+var _ = Describe("Blocks validator", func() {
+
+	It("calls create or update for all blocks within the window", func() {
+		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
+			{Number: 4},
+			{Number: 5},
+			{Number: 6},
+			{Number: 7},
+		})
+		inMemoryDB := inmemory.NewInMemory()
+		blocksRepository := &inmemory.BlockRepository{InMemory: inMemoryDB}
+		validator := history.NewBlockValidator(blockchain, blocksRepository, 2)
+
+		window := validator.ValidateBlocks()
+
+		Expect(window).To(Equal(history.ValidationWindow{LowerBound: 5, UpperBound: 7}))
+		Expect(blocksRepository.BlockCount()).To(Equal(3))
+		Expect(blocksRepository.CreateOrUpdateBlockCallCount).To(Equal(3))
+	})
+
+	It("returns the number of largest block", func() {
+		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
+			{Number: 1},
+			{Number: 2},
+			{Number: 3},
+		})
+		maxBlockNumber := blockchain.LastBlock()
+
+		Expect(maxBlockNumber.Int64()).To(Equal(int64(3)))
+	})
+})