[WIP] Add tests

[ewnd9]

I've tried to incorporate similar testing approach from pouchdb-react-native, but it turned out react-native-sqlite-storage can't be mocked.

The only way I see is to test on devices / emulators, but I don't have experience with it.

What do you think? Are you interested in testing with pouchdb tests?

[craftzdog]

Thanks for your PR and I would be glad to add tests!
It may be possible to reuse the tests of pouchdb-adapter-websql-core.

[ewnd9]

pouchdb repo uses a single test base, where different adapters are switched by environment variables in test matrix in travis-ci, so there is no specific tests for pouchdb-adapter-websql-core

[craftzdog]

It looks like the tests can't run on iOS simulator because they depend on node.js.
I think react-native-sqlite-storage shouldn't be mocked because the main purpose of the test is to make sure its stability and compatibility with pouchdb.

[craftzdog]

Maybe we can pick tests from pouchdb/tests/integration/ after removing dependencies on node.js.

[ewnd9]

Node.js shouldn't the case since pouchdb is tested in browsers too (via sauce labs)

[craftzdog]

Sorry I forgot to mention that though, unfortunately mocha doesn't work inside React Native app.
mocha is used outside of the app in every use case I found.