### Question:
UniqueColumnCombination implements Result { @Override public String toString() { return columnCombination.toString(); } protected  UniqueColumnCombination();  UniqueColumnCombination(ColumnIdentifier... columnIdentifier);  UniqueColumnCombination(ColumnCombination columnCombination); ColumnCombination getColumnCombination(); void setColumnCombination(ColumnCombination columnCombination); @Override @XmlTransient void sendResultTo(OmniscientResultReceiver resultReceiver); @Override String toString(); String toString(Map<String, String> tableMapping, Map<String, String> columnMapping); static UniqueColumnCombination fromString(Map<String, String> tableMapping, Map<String, String> columnMapping, String str); @Override int hashCode(); @Override boolean equals(Object obj);  }### Answer:
@Test public void testToString() { ColumnIdentifier expectedColumn1 = new ColumnIdentifier("table1", "column1"); ColumnIdentifier expectedColumn2 = new ColumnIdentifier("table2", "column2"); UniqueColumnCombination uniqueColumnCombination = new UniqueColumnCombination(expectedColumn1, expectedColumn2); String expectedStringRepresentation = new ColumnCombination(expectedColumn1, expectedColumn2).toString(); assertEquals(expectedStringRepresentation, uniqueColumnCombination.toString()); }