Fix testing tools, add first tests

[tiangolo]

✔️ Fix testing tools, add first tests

[codecov-io]

Codecov Report

Merging #8 into master will increase coverage by 13.37%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master       #8       +/-   ##
===========================================
+ Coverage   61.89%   75.27%   +13.37%     
===========================================
  Files           8       16        +8     
  Lines         433      554      +121     
===========================================
+ Hits          268      417      +149     
+ Misses        165      137       -28

Impacted Files	Coverage Δ
typer/testing.py	100% <ø> (ø)	⬆️
...test_tutorial/test_first_steps/test_tutorial003.py	100% <100%> (ø)
...test_tutorial/test_first_steps/test_tutorial005.py	100% <100%> (ø)
...test_tutorial/test_first_steps/test_tutorial002.py	100% <100%> (ø)
...test_tutorial/test_first_steps/test_tutorial001.py	100% <100%> (ø)	⬆️
...test_tutorial/test_first_steps/test_tutorial004.py	100% <100%> (ø)
docs/src/first_steps/tutorial004.py	100% <0%> (ø)
docs/src/first_steps/tutorial003.py	100% <0%> (ø)
... and 7 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 39e034e...45f995c. Read the comment docs.