[test] improve test for waldo. closes #584

[JanMarvin]

> packageVersion("waldo")
[1] ‘0.4.0.9000’
> devtools::test()
ℹ Testing openxlsx2
Starting 2 test processes
✔ | F W S  OK | Context
✔ |        17 | asserts [0.3s]                                                                           
✔ |         2 | base_font                                                                                
✔ |     1   0 | class-chart-sheet                                                                        
─────────────────────────────────────────────────────────────────────────────────────────────────────────
Skip (test-class-chart-sheet.R:2:1): class wbChartSheet works
Reason: empty test
─────────────────────────────────────────────────────────────────────────────────────────────────────────
✔ |         6 | class-color [0.7s]                                                                       
✔ |        27 | class-comment [0.8s]                                                                     
✔ |         5 | class-hyperlink [0.1s]                                                                   
✔ |         1 | class-sheet-data                                                                         
✔ |         9 | class-workbook-utils                                                                     
✔ |        68 | class-workbook-wrappers [13.3s]                                                          
✔ |        70 | class-workbook [1.8s]                                                                    
✔ |        10 | class-worksheet [0.2s]                                                                   
✔ |         5 | clean_sheet                                                                              
✔ |        12 | cloneWorksheet [0.4s]                                                                    
✔ |        70 | conditional_formatting [2.1s]                                                            
✔ |        11 | converters                                                                               
✔ |         6 | date_time_conversion [0.2s]                                                              
✔ |        69 | deleting_tables [0.5s]                                                                   
✔ |        12 | fill_merged_cells [0.4s]                                                                 
✔ |         7 | form_control [0.2s]                                                                      
✔ |         6 | formulas                                                                                 
✔ |        28 | freeze_pane [0.2s]                                                                       
✔ |         5 | getCellRefs                                                                              
✔ |        17 | helper_functions [0.2s]                                                                  
✔ |         2 | illegal-characters                                                                       
✔ |        15 | loading_workbook_tables [0.1s]                                                           
✔ |        53 | loading_workbook [1.3s]                                                                  
✔ |        81 | named_regions [0.9s]                                                                     
✔ |         7 | names [0.1s]                                                                             
✔ |         2 | options                                                                                  
✔ |        16 | outlines [0.3s]                                                                          
✔ |        10 | page_setup                                                                               
✔ |         3 | protect-workbook                                                                         
✔ |         3 | protect-worksheet                                                                        
✔ |        45 | pugi_cpp [0.2s]                                                                          
✔ |        85 | pugixml [0.3s]                                                                           
✔ |        22 | read_from_created_wb [0.2s]                                                              
✔ |        11 | read_write_logicals                                                                      
✔ |        13 | read_xlsx_correct_sheet [0.5s]                                                           
✔ |         4 | read_xlsx_random_seed [0.2s]                                                             
✔ |        11 | remove_worksheets [0.2s]                                                                 
✔ |        72 | save [1.7s]                                                                              
✔ |        21 | strings_xml [0.1s]                                                                       
✔ |        24 | styles_xml [0.5s]                                                                        
✔ |        12 | table_overlaps [0.4s]                                                                    
✔ |        20 | utils [0.2s]                                                                             
✔ |        17 | validate_table_name [0.2s]                                                               
✔ |        36 | wb_functions [0.6s]                                                                      
✔ |        57 | wb_styles [5.8s]                                                                         
✔ |        14 | Workbook_properties                                                                      
✔ |        24 | Worksheet_naming [0.2s]                                                                  
✔ |        52 | write [1.0s]                                                                             
✔ |         6 | writing_posixct                                                                          
✔ |         3 | xl_open                                                                                  
✔ |        50 | read_sources [46.0s]                                                                     
                                                                                                         
══ Results ══════════════════════════════════════════════════════════════════════════════════════════════
Duration: 47.1 s

── Skipped tests  ───────────────────────────────────────────────────────────────────────────────────────
• empty test (1)

[ FAIL 0 | WARN 0 | SKIP 1 | PASS 1254 ]