Move tests path under "autoload-dev".
remove missing_database.ctp

MissingDatabaseException is not part of the core anymore
add MissingDatasourceException test
Merge pull request #4289 from cakephp/3.0-composer

Move tests path under "autoload-dev".
Making Query json serializable
Adding tests for serializing a query to json
Merge pull request #4292 from antograssiot/3.0-error-template

3.0 error template
Fixed typos
Add Shell::param()
fix test
Improve docblock formatting.
Merge pull request #4300 from cakephp/3.0-fix-query-json

3.0 fix query json
Merge pull request #4301 from dereuromark/3.0-shell

Add Shell::param()