consul/state: fix for maxIndex and better tests

consul/state/state_store.go

@@ -63,9 +63,8 @@ func (s *StateStore) maxIndex(tables ...string) uint64 {
 		if err != nil {
 			panic(fmt.Sprintf("unknown index: %s", table))
 		}
-		idx := ti.(*IndexEntry).Value
-		if idx > lindex {
-			lindex = idx
+		if idx, ok := ti.(*IndexEntry); ok && idx.Value > lindex {
+			lindex = idx.Value
 		}
 	}
 	return lindex

consul/state/state_store_test.go

@@ -1012,6 +1012,11 @@ func TestStateStore_KVSSetCAS(t *testing.T) {
 	}
 	tx.Abort()
 
+	// Index was not updated
+	if idx := s.maxIndex("kvs"); idx != 0 {
+		t.Fatalf("bad index: %d", idx)
+	}
+
 	// Doing a CAS with a ModifyIndex of zero when no entry exists
 	// performs the set and saves into the state store.
 	entry = &structs.DirEntry{
@@ -1034,6 +1039,11 @@ func TestStateStore_KVSSetCAS(t *testing.T) {
 	}
 	tx.Abort()
 
+	// Index was updated
+	if idx := s.maxIndex("kvs"); idx != 2 {
+		t.Fatalf("bad index: %d", idx)
+	}
+
 	// Doing a CAS with a ModifyIndex which does not match the current
 	// index does not do anything.
 	entry = &structs.DirEntry{
@@ -1060,4 +1070,9 @@ func TestStateStore_KVSSetCAS(t *testing.T) {
 		result.ModifyIndex != 2 || string(result.Value) != "foo" {
 		t.Fatalf("bad: %#v", result)
 	}
+
+	// Index was not modified
+	if idx := s.maxIndex("kvs"); idx != 2 {
+		t.Fatalf("bad index: %d", idx)
+	}
 }