Added type hints and pytest tests

[TolstochenkoDaniil]

#373

[faif]

@TolstochenkoDaniil Can you please fix the linter errors? If it's too much work for all, at least only for the files that you modified.

[TolstochenkoDaniil]

for

@TolstochenkoDaniil Can you please fix the linter errors? If it's too much work for all, at least only for the files that you modified.

I'll check the errors, but tox completed ok before commit
Will do my best

[codecov-commenter]

Codecov Report

Merging #374 (c0677d7) into master (4fcbf1b) will increase coverage by 2.28%.
The diff coverage is 96.42%.

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
+ Coverage   30.87%   33.15%   +2.28%     
==========================================
  Files          39       39              
  Lines        1286     1306      +20     
==========================================
+ Hits          397      433      +36     
+ Misses        889      873      -16     

Impacted Files	Coverage Δ
patterns/structural/3-tier.py	0.00% <ø> (ø)
patterns/structural/front_controller.py	0.00% <ø> (ø)
patterns/behavioral/strategy.py	90.00% <96.42%> (+90.00%)	⬆️

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[faif]

Let's create a new issue for the remaining linter errors