Externalized Rcpp knitr chunk with embedded R and testthat.

#include <Rcpp.h>
using namespace Rcpp;

// Below is a simple example of exporting a C++ function to R. You can
// source this function into an R session using the Rcpp::sourceCpp 
// function (or via the Source button on the editor toolbar)

// [[Rcpp::export]]
int timesTwo(int x) {
   return x * 2;
}

/*** R
## ---- timesTwo ----
timesTwo(1)
## ----
*/

// [[Rcpp::export]]
int timesThree(int x) {
   return x * 3;
}

/*** R
## ---- timesThree ----
timesThree(1)
## ----
*/

/*** R
## ---- tests ----
require(testthat)
(expect_that( timesTwo(3), equals( timesThree(2) ) ))
(expect_that( timesTwo(6), equals( timesThree(4) ) ))
## ----
*/

And read it into the knitr environment.

````{r rcpp, include=FALSE, cache=FALSE}
Rcpp::sourceCpp("./knitrRcpp.cpp")
knitr::read_chunk("./knitrRcpp.cpp")
````

---

Now the named knitr chunks in the embedded R can be used as named chunks.

````{r timesTwo}
````

timesTwo(1)

## [1] 2

````{r timesThree}
````

timesThree(1)

## [1] 3

````{r tests, eval=FALSE}
````

````{r tests, echo=FALSE, collapse=TRUE}
````

require(testthat)
(expect_that( timesTwo(3), equals( timesThree(2) ) ))
(expect_that( timesTwo(6), equals( timesThree(4) ) ))

## As expected: timesTwo(3) equals timesThree(2)
## As expected: timesTwo(6) equals timesThree(4)