README.md

In skranz/testexamples: Test a package by running and comparing examples

output: html_document: keep_md: yes

Tools for testing packages by comparing results from examples

The standard approach of unit testing, e.g. via testthat is to write explicit test commands, like

test_that("Distinct roots", {

    roots <- real.roots(1, 7, 12)

    expect_that( roots, is_a("numeric") )
    expect_that( length(roots), equals(2) )
    expect_that( roots[1] < roots[2], is_true() )
})

Copied from this blog entry on testing.

While very useful, writing comprehensive tests is also quite time intensive. While my packages don't currently have such tests, they have a lot of examples, partly in separate R files, partly inside vignettes.

If these examples worked correctly in a previous version of my package one way of testing a new package version is that all those examples again run without error and yield the same results as earlier (unless I changed something on purpose that would cause different results).

The package testexamples shall help to test your package using your examples. Install it from Github via:

devools::install_github("skranz/testexamples")

Below is a simple illustration.

# Assume f is a function in your package
f = function(x) {
  x
}

# Some example code
code = "
f(1)
f(2)
f(3)
"

library(testexamples)

# Specify all example sources. Can be files
# or direct code as strings.
sources = example.sources(ex.text=c(myexample=code))

# Create an example test object by running
# all examples. It uses all objects from
# the global environment and currently loaded
# packages.
et = create.example.tests(sources)

# You may want to save et somewhere
# saveRDS(et, "example_tests.Rds")

Let us mimick a change in the package by changing the function f:

f = function(x) {
  if (x==2) stop("Error")
  x*x
}

# Load old example test
# et = readRDS("example_tests.Rds")

# Evaluate all examples again
# and compare with previous results
run.example.tests(et)

## 
## 2 issues found when testing examples. See log in
## example_test_log.Rmd

The created log file example_test_log.Rmd would looks as follows:

Comparison of examples

2019-11-27 14:57:45 (new) vs 2019-11-27 14:57:45 (old)

my_example

```{r eval=FALSE} f(1) f(2)

!! THROWS NEW ERROR !!

f(3)

RESULTS DIFFER

```

skranz/testexamples documentation built on Nov. 28, 2019, 12:12 a.m.