Check for accidental extraneous dependencies in end-to-end-tests

[gaearon]

See the discussion in #1685 (comment).
@lpalmes might want to work on this so please don’t jump on the issue yet unless you’re @lpalmes.

[lpalmes]

@gaearon @Timer,
I've been testing some awk commands a bit

$ awk '/dependencies/{y=1;next}/},/{y=0; next}y' package.json
    "react": "^15.4.2",
    "react-dom": "^15.4.2"
$ awk '/devDependencies/{y=1;next}/},/{y=0; next}y' package.json
    "react-scripts": "0.9.4"

This will get between the word dependencies and the closing bracket below the dependencies, i only need to check if every dependency is correct.
If you have any ideas how to do this let me know, i was thinking it could be possible to partly match each line to react

[Timer]

I've been a bit busy, @lpalmes -- sorry for not giving you a quicker response.
We can probably grep inverted what comes back from that, validating they're packages we want:

awk '/dependencies/{y=1;next}/},/{y=0; next}y' package.json | \
  grep -v -q -E '^\s*"react(?:-dom|-scripts)?"'

-v is invert match & -q is quiet -- we only care about the return code .

Then just test to make sure the result of that is not 0, because 0 would mean it found something extraneous!

[Timer]

@lpalmes Hi! How's everything going?
Would you like to finish this? 😄 If you're too short on time, that's alright too.

[lpalmes]

I was traveling, got back yesterday, sorry for the absence.
I will add it today, i let you know otherwise today @Timer

[Timer]

Sweet, thanks @lpalmes!
Hope you enjoyed your travels & were safe! 😄

[lpalmes]

Thanks @Timer, i've enjoyed it and managed to meet lot of developers and companies, just what i was looking for 😄 , really great experience.
I've just sent the pull request to fix this. I've tried on my computer, and it worked quite nicely. I've added some random deps to package.json and confirmed that errors correctly.