adjust all for review, create test files

Former-commit-id: ff13be57aab24129a97f359464fb5b8154c5a206 [formerly ff9566d3bd5653b23fc2846b26e1b07a15fdc159]
Former-commit-id: 371821f0ad0bb76640eed2199f5dc49f979d14d8

sharding/collator.go

@@ -9,7 +9,7 @@ import (
 	"math/big"
 )
 
-// subscribeBlockHeaders checks incoming block headers and determines if
+// SubscribeBlockHeaders checks incoming block headers and determines if
 // we are an eligible proposer for collations. Then, it finds the pending tx's
 // from the running geth node and sorts them by descending order of gas price,
 // eliminates those that ask for too much gas, and routes them over

sharding/collator_test.go

@@ -1,19 +1,29 @@
 package sharding
 
 import (
-	"github.com/ethereum/go-ethereum/common/hexutil"
-	"sync"
+	"context"
+	"fmt"
 	"testing"
+
+	"github.com/ethereum/go-ethereum/core/types"
 )
 
-// FakeEthService based on implementation of internal/ethapi.Client
-type FakeEthService struct {
-	mu sync.Mutex
+type FakeClient struct {
+	client *FakeEthClient
+}
 
-	getCodeResp hexutil.Bytes
-	getCodeErr  error
+type FakeEthClient struct{}
+
+type FakeSubscription struct{}
+
+func (ec *FakeEthClient) SubscribeNewHead(ctx context.Context, ch chan<- *types.Header) (FakeSubscription, error) {
+	return FakeSubscription{}, fmt.Errorf("error, network disconnected!")
 }
 
 func TestSubscribeHeaders(t *testing.T) {
-
+	client := &FakeClient{client: &FakeEthClient{}}
+	err := subscribeBlockHeaders(client)
+	if err != nil {
+		t.Errorf("subscribe new headers should work", "no error", err)
+	}
 }