Extract storage diff fetching behind an interface

- Replaces directly reading from a CSV
- Simplifies testing
- Should hopefully make it easier to plug in other sources for storage
  diffs (e.g. differently formatted CSVs, JSON RPC, etc)

libraries/shared/mocks/converter.go

@@ -53,6 +53,6 @@ func (converter *MockConverter) SetToEntityConverterError(err error) {
 	converter.entityConverterError = err
 }
 
-func (c *MockConverter) SetToModelConverterError(err error) {
-	c.modelConverterError = err
+func (converter *MockConverter) SetToModelConverterError(err error) {
+	converter.modelConverterError = err
 }

libraries/shared/mocks/storage_fetcher.go

@@ -0,0 +1,23 @@
+package mocks
+
+import "github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+
+type MockStorageFetcher struct {
+	RowsToReturn []utils.StorageDiffRow
+	ErrsToReturn []error
+}
+
+func NewMockStorageFetcher() *MockStorageFetcher {
+	return &MockStorageFetcher{}
+}
+
+func (fetcher *MockStorageFetcher) FetchStorageDiffs(out chan<- utils.StorageDiffRow, errs chan<- error) {
+	for _, err := range fetcher.ErrsToReturn {
+		errs <- err
+	}
+	for _, row := range fetcher.RowsToReturn {
+		out <- row
+	}
+	close(out)
+	close(errs)
+}

libraries/shared/mocks/storage_queue.go

@@ -23,9 +23,11 @@ import (
 type MockStorageQueue struct {
 	AddCalled bool
 	AddError  error
+	PassedRow utils.StorageDiffRow
 }
 
 func (queue *MockStorageQueue) Add(row utils.StorageDiffRow) error {
 	queue.AddCalled = true
+	queue.PassedRow = row
 	return queue.AddError
 }