week2-assignments.Rmd

---
title: "ggplot-testi"
author: "Tim Dennis"
date: "January 9, 2016"
output: html_document
---
```{r}
library(testit)
library(ggplot2)
library(testthat)
gapminder <- read.csv("data/gapminder-FiveYearData.csv", header=TRUE)

```

Create a ggplot object. 

```{r}
# create a ggplot assign t
w2a1 <- ggplot(data = gapminder, aes(x=year, y=lifeExp, by=country, color=continent)) +
  geom_line()
```

The object returned by ggplot has many different sub-lists you can grab. Lots of things to choose to test for grading. 

```{r}
str(w2a1)
```

Test using testit package. 

```{r testit}
assert("is not labeled year", "year" == w2a1$labels$x[1])
assert("number rows in data is not 1704", 1704 == nrow(w2a1$data))
## Invisible NULL if all expressions returned TRUE, otherwise an error is signalled and the user-provided message is emitted.
#if false, would throw error (not executed here b/c would stop rmarkdown build)
assert("number rows in data is 1704", 1705 == nrow(w2a1$data))

```

Test using testthat package. 

```{r testthat}

#expect_that(w2a1, is_a("lm"))
#Error: w2a1 inherits from gg, ggplot not lm

expect_that(w2a1, is_a('lm'))

expect_that("year", equals(w2a1$labels$x[1]))

expect_that(str(w2a1$facet), prints_text("List of 1"))


```