feat: hide postpone button if happens date absent or invalid

[ilandikov]

Description

Change shouldShowPostponeButton() to account for valid happens dates.

Motivation and Context

Improve postpone usability: do not show postpone button when it is useless.

How has this been tested?

Unit tests + exploratory feature tests.

Screenshots

Postpone button is absent for tasks 5-9.

NOTE: this screenshot is taken without scheduled date inference.

Types of changes

Changes visible to users:

• New feature (prefix: feat - non-breaking change which adds functionality)

Checklist

• My code follows the code style of this project and passes yarn run lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
  • documentation for postponement is absent for now
• My change has adequate Unit Test coverage.

Terms

• My contribution follow this project's contributing guide
• I agree to follow this project's Code of Conduct

[claremacrae]

Looks good to me.

[ilandikov]

Looks good to me.

Thanks. I added a screenshot and NOTE: this screenshot is taken without scheduled date inference.

[claremacrae]

Thanks. There is no need to change the screenshot, but task 8 behaves that way because it has no date, not an invalid one. As a 5 digit year will not be recognised as a date.

[claremacrae]

Thanks!

[claremacrae]

I did some more exploratory testing of this, and realised that there are cases we didn't think of to test - and define the behaviour we want - like what if:

• there is a valid due date, but invalid scheduled?
• there is a invalid due date, but a valid scheduled?

Basically, note to self: remember not to test just the simple cases, but try and remember to exploratory-test the more complex related cases for desired behaviour, and cover them in automated tests too.

I've made a note in the Development Discussion to come back to this...