Fixed missing dependency to pytest

[Tom-Kingstone]

NOTE: Depends on

Issues addressed by this PR

Closes #180

Test files

run run_tests.bat after install and see that the tests run.

Changelog

Additional comments

[Tom-Kingstone]

@BHoMBot check required

[bhombot-ci]

@Tom-Kingstone to confirm, the following actions are now queued:

• check code-compliance
• check documentation-compliance
• check project-compliance
• check core
• check null-handling
• check serialisation
• check versioning
• check installer

[Tom-Kingstone]

@BHoMBot check copyright-compliance

[bhombot-ci]

@Tom-Kingstone to confirm, the following actions are now queued:

• check copyright-compliance

There are 16 requests in the queue ahead of you.

[Dmamedova]

Installation was successful and all tests passed

[Tom-Kingstone]

@BHoMBot check ready-to-merge

[bhombot-ci]

@Tom-Kingstone to confirm, the following actions are now queued:

• check ready-to-merge

[bhombot-ci]

@Tom-Kingstone just to let you know, I have provided a check-ready-to-merge result to this Pull Request as it was detected to be linked to other Pull Requests in a series. The comment which triggered this check came from @Tom-Kingstone on LadybugTools_Toolkit