Introduction to PivotalR testing

PivotalR tests are built upon the 'testthat' package by Hadley Wickham [1].
Instructions for using this package can be found in the
[Testing](http://r-pkgs.had.co.nz/tests.html) chapter of
[R packages](http://r-pkgs.had.co.nz/).

Given below is the quick-start guide:

- Most PivotalR tests require a database connected on localhost. The tests
require two variables set to ensure connection to local database:
    - `pivotalr_dbname`: Name of the test database
    - `pivotalr_port`: Port of the test database

- Use devtools::test() to run the tests. This function needs to be called from the
root folder of PivotalR. Alternatively, `pkg` parameter can be set to the exact
location of the package and `filter` parameter can be used to run specific tests.
See the testthat documentation for details on the parameters.

- `testthat` will run all (or filtered) test files in the `tests/testthat`
folder that start with the specific text `test`.

-  In the tests, one can use the data sets "abalone" and "null.data",
which are included in the PivotalR package. Please refer to the user
manual for the details about these two data sets.


- Additional data set files in the tests should by placed outside of PivotalR
  package, and the path of the data sets be passed into the tests as an
  environment parameter. This is enforced since CRAN has a size
  limitation for the package size. In general, it is not recommended to
  use additional data files within PivotalR, rather place data in the
  database and let PivotalR access it through DB API.