### Question:
ExcelMatrixWriter implements IMatrixWriter { @Override public void flush() { } ExcelMatrixWriter(String fileName, boolean useXlsx);  ExcelMatrixWriter(OutputStream outputStream, boolean useXlsx);  ExcelMatrixWriter(String fileName, boolean useXlsx, String sheetName);  ExcelMatrixWriter(OutputStream outputStream, boolean useXlsx, String sheetName); @Override void writeCells(SimpleCell[] cells); @Override void write(String[] strings); @Override void close(); @Override void flush();  }### Answer:
@Test public void testFlush() { assert true; }