Add AddwCommandTest

[jowhee3011]

• Not entirely covered by 85% of methods covered
• One method is commented out, will try to figure it out asap
• Fix AddwCommandParserTest

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...java/seedu/address/logic/commands/AddwCommand.java	85.71%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...java/seedu/address/logic/commands/AddwCommand.java	65.95% <85.71%> (+44.00%)	19.00 <0.00> (+16.00)

... and 11 files with indirect coverage changes