Update tests for appointment commands

[licongshen12]

Fixes #249

[codecov]

Codecov Report

Merging #243 (74f0f3d) into master (1c8e4ff) will increase coverage by 3.74%.
Report is 5 commits behind head on master.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #243      +/-   ##
============================================
+ Coverage     74.84%   78.59%   +3.74%     
- Complexity      767      827      +60     
============================================
  Files           125      125              
  Lines          2461     2490      +29     
  Branches        240      244       +4     
============================================
+ Hits           1842     1957     +115     
+ Misses          511      431      -80     
+ Partials        108      102       -6     

Files	Coverage Δ
...ava/seedu/address/logic/commands/ClearCommand.java	100.00% <100.00%> (ø)
...java/seedu/address/logic/commands/ExitCommand.java	100.00% <100.00%> (ø)
...java/seedu/address/logic/commands/HelpCommand.java	100.00% <100.00%> (ø)
...java/seedu/address/logic/commands/ListCommand.java	100.00% <100.00%> (ø)
...java/seedu/address/logic/commands/ModeCommand.java	100.00% <100.00%> (ø)

... and 22 files with indirect coverage changes

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[trgao]

LGTM