add tests

weed/shell/command_volume_balance_test.go

@@ -1,6 +1,8 @@
 package shell
 
 import (
+	"github.com/chrislusf/seaweedfs/weed/storage/types"
+	"github.com/stretchr/testify/assert"
 	"testing"
 
 	"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
@@ -181,3 +183,14 @@ func TestBalance(t *testing.T) {
 	}
 
 }
+
+func TestVolumeSelection(t *testing.T) {
+	topologyInfo := parseOutput(topoData)
+
+	vids, err := collectVolumeIdsForTierChange(nil, topologyInfo, 1000, types.ToDiskType("hdd"), "", 20.0, 0);
+	if err != nil {
+		t.Errorf("collectVolumeIdsForTierChange: %v", err)
+	}
+	assert.Equal(t, 378, len(vids))
+
+}