@Test
public void merge() {

    final HashMap<InterpolationVariable, Integer> map = new HashMap<>();
    map.put(new InterpolationVariable("var",
                                      DataType.TYPE_DATE,
                                      "Person",
                                      "birthday"), 1);
    map.put(new InterpolationVariable("var",
                                      DataType.TYPE_DATE,
                                      "Person",
                                      "dateOfDeath"), 2);
    final Map<InterpolationVariable, Integer> result = new InterpolationVariableCollector(map).getMap();
    assertEquals(1, result.size());
    final InterpolationVariable var = result.keySet().iterator().next();
    assertEquals("var", var.getVarName());
    assertEquals(DEFAULT_TYPE, var.getDataType());
}