### Question:
FunctionalDependencyVisualization { protected ColumnIdentifier getColumnIdentifier(Set<ColumnCombination> columnCombinations, int index, int columnIndex) { int curIndex = -1; for (ColumnCombination combination : columnCombinations) { curIndex++; if (curIndex != index) { continue; } int curColumnIndex = -1; for (ColumnIdentifier columnIdentifier : combination.getColumnIdentifiers()) { curColumnIndex++; if (curColumnIndex == columnIndex) { return columnIdentifier; } } } return null; } FunctionalDependencyVisualization(List<FunctionalDependencyResult> results,
                                           TableInformation tableInformation); void createVisualizationData(); @SuppressWarnings(Constants.SUPPRESS_WARNINGS_UNCHECKED) void printFunctionalDependencyVisualizationData(
    Map<ColumnIdentifier, Set<ColumnCombination>> dependantMap); String unifyPath(String path); String combinePaths(String dirPath, String filePath);  }### Answer:
@Test public void testGetColumnIdentifier() { TableInformation tableInformation = tableInformationMap.values().iterator().next(); FunctionalDependencyVisualization visualization = new FunctionalDependencyVisualization( functionalDependencyResults, tableInformation); ColumnIdentifier expectedColumnIdentifier = new ColumnIdentifier("expect", "expect"); ColumnCombination combination1 = new ColumnCombination( new ColumnIdentifier("1", "1"), new ColumnIdentifier("1", "2")); ColumnCombination combination2 = new ColumnCombination( expectedColumnIdentifier, new ColumnIdentifier("f", "f")); ColumnCombination combination3 = new ColumnCombination( new ColumnIdentifier("1", "5"), new ColumnIdentifier("2", "2"), expectedColumnIdentifier); Set<ColumnCombination> columnCombinations = new TreeSet<>(); columnCombinations.add(combination1); columnCombinations.add(combination2); columnCombinations.add(combination3); ColumnIdentifier actualColumnIdentifier = visualization.getColumnIdentifier(columnCombinations, 2, 2); assertEquals(expectedColumnIdentifier, actualColumnIdentifier); actualColumnIdentifier = visualization.getColumnIdentifier(columnCombinations, 1, 0); assertEquals(expectedColumnIdentifier, actualColumnIdentifier); }