Generator cleanup with tests

[mrhardikjoshi]

This PR introduces tests on top of changes of #1716

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (f86d54c) 93.12% compared to head (e496b98) 93.08%.

❗ Current head e496b98 differs from pull request most recent head 2d2f968. Consider uploading reports for the commit 2d2f968 to get more accurate results

Files	Patch %	Lines
lib/active_graph/railtie.rb	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##               11    #1717      +/-   ##
==========================================
- Coverage   93.12%   93.08%   -0.04%     
==========================================
  Files         128      128              
  Lines        5700     5700              
==========================================
- Hits         5308     5306       -2     
- Misses        392      394       +2     

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[mrhardikjoshi]

update readme file to include command/steps to run e2e tests

[klobuczek]

Great job!

[mrhardikjoshi]

To Do Notes:

1. add tests for down migration command
2. add tests for running default rails tests in minitest
3. cleanup and merge both github workflows