Test fixes for hw branch

this method returns twice longer string, like:
```java
text = "agregator-coord16-e67506c6-b5e8-4090-9415-7fd46d474c6d-df91f004-597b-41d3-a789-adc590f95f4e/2014-06-27T13:20Zagregator-coord16-e67506c6-b5e8-4090-9415-7fd46d474c6d-df91f004-597b-41d3-a789-adc590f95f4e/2014-06-27T13:20Z"
```

produce fail of `testGraphVertices()`

also fixed in #305