### Question:
PrintPayload implements Jsonable { public TextRow appendLineOfChar(int columns, String character) { String line = character; while (line.length() < columns) { line += character; } return append(line); } PrintPayload();  PrintPayload(String printerId); TextRow append(String text); TextRow append(String text, PrinterFont printerFont); void append(PrintPayload toAppendPayload); void appendEmptyLine(); TextRow appendLineOfChar(int columns, String character); TextRow appendLeftRight(int columns, String left, String right); ImageRow append(Bitmap image); ImageRow append(Bitmap image, boolean scaleToFit); PrintRow[] getRows(); int getCodePage(); void setCodePage(int codePage); String getLanguage(); void setLanguage(String languageCode); void setPrinterId(String printerId); String getPrinterId(); boolean hasPrinterId(); @Override String toJson(); static PrintPayload fromJson(String json);  }### Answer:
@Test public void checkAppendLineOfChar() { PrintPayload payload = new PrintPayload(); TextRow row = payload.appendLineOfChar(30, "="); assertThat(row.getText()).isEqualTo("=============================="); }