use testify

[arxdsilva]

fixes #218

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Short description of what this PR does:

• This starts the change requested in Replace 'testing' with Testify #218 to use assertions instead of standard testing package on test files.

[arxdsilva]

hi @thinkingserious , I've been adding the error messages to the testify assertions, but they seem redundant, do you think that it's best to remove them all or just keep them?

[codecov]

Codecov Report

Merging #269 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #269   +/-   ##
=======================================
  Coverage   70.95%   70.95%           
=======================================
  Files           3        3           
  Lines         451      451           
=======================================
  Hits          320      320           
  Misses        127      127           
  Partials        4        4

---

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 8cb43f4...f728210. Read the comment docs.

[thinkingserious]

Hello @arxdsilva,

Thanks again for the PR!

It's HACKTOBERFEST! We want to show our appreciation by sending you some special Hacktoberfest swag. If you have not already, could you please fill out this form so we can send it to you? Thanks!

Team SendGrid DX

[thinkingserious]

Congrats @arxdsilva! You are first on the leaderboard: https://dx.sendgrid.com/hacktoberfest :)