Improve tests because of more robust macro

[eirnym]

Closes #4

Notes on implementation and differences with proposition:

Name generation:

• There's no special subtest variant
• There's no tests which has specifications for encoding or endian
• Error list is limited separated out by it's own id
• Error id is included in function name for read-rejected tests.
• Actual constant name generation is slightly changed from proposed

Test data and metadata:

• Documentation should be implemented per-test-case if any.
• Data split into 3 files:
  • layouts — common for every test
  • accepted — data for r/w accepted tests
  • rejected — data for read rejected tests
  • Data for write rejected tests is not separated out because there's only 3 strings

Possible future to-do (low priority):

• per-test-case documentation — could be done as module documentation where data is located
• More information on reasoning of write-io-rejected tests.
• extract actual functions? This would potentially work only for for accepted tests for read/write.

You're welcome to create PR if any additional work on tests is needed, including list from possible future to-do list.

[github-actions]

	Tests	Passed ✅	Skipped	Failed
Deku String	292 ran	292 passed	0 skipped	0 failed

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
201	201	100%	0%	🟢

New Files

No new covered files...

Modified Files

No covered modified files...

updated for commit: f102303 by action🐍