Refactor unit tests

[Thanhphan1147]

Overview

Relates to #19, rewrite unit tests to :

• Directly set up the test charm in the test function
• Write files to the charm's containers directly instead of using push/pull mocks

Rationale

This makes the test functions easier to understand, avoid complicated fixture dependencies

Juju Events Changes

N/A

Module Changes

N/A

Library Changes

N/A

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Manging Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex)

[arturo-seijas]

LGTM

[amandahla]

LGTM!

[github-actions]

Test coverage for 5b47b6d

Name                            Stmts   Miss Branch BrPart  Cover   Missing
---------------------------------------------------------------------------
src/actions/__init__.py             3      0      0      0   100%
src/actions/register_user.py       21      0      2      0   100%
src/actions/reset_instance.py      21      3      2      1    83%   54-58
src/charm.py                      107      4     14      1    96%   108-109, 161-162
src/charm_state.py                 57      2     10      2    94%   22, 85
src/charm_types.py                 11      0      0      0   100%
src/database_client.py             53      1     10      3    94%   35, 47->exit, 69->exit
src/database_observer.py           54      4      6      0    93%   70-72, 88
src/exceptions.py                   4      0      0      0   100%
src/mjolnir.py                     94      2     22      4    95%   68, 80->exit, 116, 164->169
src/observability.py                9      0      0      0   100%
src/pebble.py                      73      4      2      1    93%   90-91, 109-110
src/saml_observer.py               45      1      8      0    98%   64
src/synapse/__init__.py             3      0      0      0   100%
src/synapse/api.py                161      5     20      2    96%   144, 315, 399-401
src/synapse/workload.py           171      8     20      4    94%   208-209, 245-246, 262, 292->295, 311->314, 350, 481-486
src/user.py                        24      0      4      0   100%
---------------------------------------------------------------------------
TOTAL                             911     34    120     18    95%

Static code analysis report

Run started:2023-09-25 14:10:58.721948

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 4261
  Total lines skipped (#nosec): 7
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):