public void Excel_TestsMoreLetters()
 {
     int column_number = 18280;
     string expected_result = "AAAB";
     Excel_CalculateColumnName calculateColumnName = new Excel_CalculateColumnName();
     string result = calculateColumnName.ColumnName(column_number);
     Assert.AreEqual(expected_result, result);
 }
 public void Excel_TestOneLetterDiffZ()
 {
     int column_number = 1;
     string expected_result = "A";
     Excel_CalculateColumnName calculateColumnName = new Excel_CalculateColumnName();
     string result = calculateColumnName.ColumnName(column_number);
     Assert.AreEqual(expected_result, result);
 }
 public void Excel_InvalidColumnNumber()
 {
     int column_number =0;
     string expected_result = "-1";
     Excel_CalculateColumnName calculateColumnName = new Excel_CalculateColumnName();
     string result = calculateColumnName.ColumnName(column_number);
     Assert.AreEqual(expected_result, result);
 }