---
title: "Getting Started"
vignette: >
%\VignetteIndexEntry{Getting started}
%\VignetteEngine{knitr::rmarkdown}
\usepackage[utf8]{inputenc}
---
## A very simple example
Suppose you have a file ``biggest.R`` with the following function:
```{r}
biggest <- function(x,y) {max(c(x,y))}
```
To test this create a file called ``test_biggest.R`` in the same directory containing:
```{r, eval=FALSE}
library(unittest, quietly = TRUE)
source('biggest.R')
ok(biggest(3,4) == 4, "two numbers")
ok(biggest(c(5,3),c(3,4)) == 5, "two vectors")
```
Now in an ``R`` session ``source`` the test file:
```{r, eval=FALSE}
source('test_biggest.R')
```
and you will see output like this
```
ok - two numbers
ok - two vectors
```
and that's it.
Now each time you edit ``biggest.R`` re-sourcing ``test_biggest.R``
reloads your function and runs your unit tests.
## Comparing results
Suppose our ``biggest`` function was broken, for example:
```{r}
biggest <- function(x,y) { 4 }
```
Our tests from earlier would return:
```
ok - two numbers
not ok - two vectors
# Test returned non-TRUE value:
# [1] FALSE
```
It would be more useful if we saw what ``biggest()`` actually returned, to help
work out the problem.
To help with this we can use ``ut_cmp_equal``. If we rewrite our test to:
```{r, eval=FALSE}
library(unittest, quietly = TRUE)
source('biggest.R')
ok(ut_cmp_equal(biggest(3,4), 4), "two numbers")
ok(ut_cmp_equal(biggest(c(5,3),c(3,4)), 5), "two vectors")
```
Now the test output shows what we did get (in red) and what we expected (in green):
ok - two numbers
not ok - two vectors
# Test returned non-TRUE value:
# Mean relative difference: 0.25
# --- biggest(c(5, 3), c(3, 4))
# +++ 5
# [1] [-4-]{+5+}

This is particularly useful when there are many values returned:
> ok(ut_cmp_equal(c(1,2,3,4,5), c(1,8,8,4,5)))
not ok - ut_cmp_equal(c(1, 2, 3, 4, 5), c(1, 8, 8, 4, 5))
# Test returned non-TRUE value:
# Mean relative difference: 2.2
# --- c(1, 2, 3, 4, 5)
# +++ c(1, 8, 8, 4, 5)
# [1] 1 [-2 3-]{+8 8+} 4 5