refactor(e2e): turn repeated test (build and start) into function

[Jiansen]

There are 3 build-and-start tests in the current e2e.sh.

I placed repeated code in a function.

In the first test, if there is a reason why npm start -- --smoke-test should run before npm run build, I will extract npm start -- --smoke-test out of function build_check.

[mxstbr]

TIL you can have functions in bash scripts!

[Jiansen]

TIL you can have functions in bash scripts!

@mxstbr , I leant from @ltk ( #244 ) just a few days ago :-)

[gaearon]

When would it be empty? We seem to always pass it.

[Jiansen]

Yes, we always passed in snap file path in the 3 tests.

I am thinking what the build_check should behave when it is called without given $1.

-- option 1: delete the if check, let the function fall and let developer knows that Jest test is mandatory
-- option 2: use the following code, skip Jest test when there is no $1

if [ -z "$1" ]
    then
      test -e $1
fi

I will update the code when received your suggestion.

[gaearon]

This is just an end-to-end test that we run for this tool, the developer won’t see it.
So relying on jest existing is fine here.

[gaearon]

Thanks again for the PR. Sorry it’s getting out of date. There are a few more important changes I wanted to get in first but I’m keeping an eye on this one. It should be good to go after #419 is merged so I’ll get back to it and ask you to update 😄 . Thank you!

[Jiansen]

This PR is to clean up e2e.sh. It makes sense to do this after other important changes.

[gaearon]

I’m closing because this got out of date.
I’ll be happy to merge it if you rebase, so feel free to send another PR!
Thank you for your contributions.