This had been intended to get 100% coverage for TextData functions, and it does that.
However, some minor bugs requiring source changes arose during testing.
- the Excel CHAR function restricts its argument to 1-255. PhpSpreadsheet CHARACTER
had been allowing 0+. Also, there is no need to test if iconv exists,
since it is part of Composer requirements.
- The DOLLAR function had been returning NUM for invalid arguments. Excel returns VALUE.
Also, negative amounts were not being handled correctly.
- The FIXEDFORMAT function had been returning NUM for invalid arguments. Excel FIXED returns VALUE.