unitizer simplifies creating, reviewing, and debugging unit tests in R. To install:
Please keep in mind this is an experimental framework that has been thoroughly tested by one person.
unitizer bakes in a lot of contextual help so you can get started without reading all the documentation. Try the demo to get an idea:
Or check out the screencast to see
unitizer in action.
Why Another Testing Framework?
Automated Test Formalization
Are you tired of the
dput then copy-paste R objects into test file
dance, or do you use
testthat::expect_equal_to_reference a lot?
unitizer you review function output at an interactive prompt as you
would with informal tests. You then store the value, conditions (e.g.
warnings, etc.), and environment for use as the reference values in formal
tests, all with a single keystroke.
Do you wish the nature of a test failure was more immediately obvious?
When tests fail, you are shown a proper diff so you can clearly identify how the test failed:
Do you wish that you could start debugging your failed tests without additional set-up work?
unitizer drops you in the test environment so you can debug why the test
failed without further ado:
Fast Test Updates
Do you avoid improvements to your functions because that would require painstakingly updating many tests?
The diffs for the failed tests let you immediately confirm only what you intended changed. Then you can update each test with a single keystroke.
unitizer stores R expressions and the result of evaluating them so that it can
detect code regressions. This is akin to saving test output to a
.Rout.save file as documented in Writing R
except that we're storing the actual R objects and it is much easier to review
- Write test expressions as you would when informally testing code on the command line, and save them to a file (e.g. "my_file_name.R")
unitize("my_file_name.R")and follow the prompts
- Continue developing your package
unitize("my_file_name.R"); if any tests fail you will be able to review and debug them in an interactive prompt
unitizer can run in a non-interactive mode for use with
R CMD check.
help(package="unitizer"), in particular
vignette("unitizer")for a list of vignettes, or skip straight to the Introduction vignette
unitizer Differ from
unitizer requires you to review test outputs and confirm they are as expected.
testthat requires you to assert what the test outputs should be beforehand.
There are trade-offs between these strategies that we illustrate here, first
vec <- c(10, -10, 0, .1, Inf, NA) expect_error( log10(letters), "Error in log10\\(letters\\) : non-numeric argument to mathematical function\n" ) expect_equal(log10(vec), c(1, NaN, -Inf, -1, Inf, NA)) expect_warning(log10(vec), "NaNs produced")
vec <- c(10, -10, 0, .1, Inf, NA) log10(letters) # input error log10(vec) # succeed with warnings
These two unit test implementations are functionally equivalent. There are benefits to both approaches. In favor of
- Tests are easy to write
- Conditions are captured automatically, with no need for special handling
- You can immediately review failing tests in an interactive environment
- Updating tests when function output legitimately changes is easy
In favor of
- The tests are self documenting; expected results are obvious
- Once you write the test you are done; with
unitizeryou still need to
unitizeand review the tests
unitizer is particularly convenient when the tests return complex objects (e.g
lm does) or produce conditions. There is no need for complicated
assertions involving deparsed objects.
testthat tests to
If you have a stable set of tests it is probably not worth trying to convert them to
unitizer unless you expect the code those tests cover to change substantially. If you do decide to convert tests you can use the provided
testthat_translate* functions (see
unitizer and Packages
The simplest way to use
unitizer as part of your package development process is to create a
tests/unitizer folder for all your
unitizer test scripts. Here is a sample test structure from the demo package:
unitizer.fastlm/ # top level package directory R/ tests/ run.R # <- calls `unitize` or `unitize_dir` unitizer/ fastlm.R cornerCases.R
And this is what the
tests/run.R file would look like
library(unitizer) unitize("unitizer/fastlm.R") unitize("unitizer/cornerCases.R")
The path specification for test files should be relative to the
directory as that is what
R CMD check uses. When
unitize is run by
check it will run in a non-interactive mode that will succeed only if all tests
You can use any folder name for your tests, but if you use "tests/unitizer"
unitize will look for files automatically, so the following work assuming your
working directory is a folder within the package:
unitize_dir() # same as `unitize_dir("unitizer")` unitize("fast") # same as `unitize("fastlm.R")` unitize() # Will prompt for a file to `unitize`
Remember to include
unitizer as a "suggests" package in your DESCRIPTION file.
Things You Should Know About
unitizer Writes To Your Filesystem
unitized tests need to be saved someplace, and the default action is to save to the same directory as the test file. You will always be prompted by
unitizer before it writes to your file system. See storing
unitized tests for implications and alternatives.
Tests Pass If They
all.equal Stored Reference Values
Once you have created your first
unitize, subsequent calls to
unitize will compare the old stored value to the new one using
all.equal. You can change the comparison function by using
unitizer_sect (see tests vignette).
Increase Reproducibility with Advanced State Management
unitizer can track and manage many aspects of state to make your tests more
reproducible. For example,
unitizer can reset your search path to what is
is found in a fresh R session prior to running tests to avoid conflicts with
whatever libraries you happen to have loaded at the time. Your session state is
unitizer exits. The following aspects of state can be actively
tracked and managed:
- Search path (including removing the global environment from search path)
- Random seed
- Working directory
- Loaded namespaces
State management is turned off by default because it requires tracing some base
functions which is against CRAN policy. If you wish to enable this feature use
unitize(..., state='recommended') or
For more details see
?unitizerState and the reproducible tests
Beware of Force Quitting from
If you interrupt evaluation with CTRL+C (or with ESC in RStudio), or if you
debug and quit with 'Q', you will exit
unitizer with no
opportunity to save any modifications you made during
unitizer review. Make
sure you quit by typing 'Q' at the
unitizer prompt. If you are in
you will need to let the browsed function finish evaluation to return to the
unitizer prompt, and only then quit.
Tests that modify objects by reference are not perfectly suited for use with
unitizer. The tests will work fine, but
unitizer will only be able to show you the most recent version of the reference object when you review a test, not what it was like when the test was evaluated. This is only an issue with reference objects that are modified (e.g. environments, RC objects,
data.table modified with
unitizer Is Complex
In order to re-create the feel of the R prompt within
unitizer we resorted to a fair bit of trickery. For the most part this should be transparent to the user, but you should be aware it exists in the event something unexpected happens that exposes it. Here is a non-exhaustive list of some of the tricky things we do:
- Each tests is evaluated in its own environment, a child of the previous test's environment; because R looks up objects in parent environments it appears that all tests are evaluated in one environment (see interactive environment vignette)
- We provide modified versions of
ls(see esoteric topics vignette) at the
tracebackshould work when reviewing tests that produce errors, but only because we capture the trace with
sys.callsand write it to
- We sink
stderrduring test evaluation to capture those streams (see details on tests vignette), though we take care to do so responsibly
- We parse the test file and extract comments so that they can be attached to the correct test for review
- The history file is temporary replaced so that your
unitizerinteractions do not pollute it
Avoid Tests That Require User Input
In particular, you should avoid evaluating tests that invoke
functions, or introducing interactivity by using something like
readline, or some such. Tests will work, but the
interaction will be challenging because you will have to do it with
Doing so will cause
unitize to quit if any test expressions throw conditions. See discussion in error handling.
Some Base Functions are Masked at the
quit are masked to give the user an opportunity to cancel the quit
action in case they meant to quit from
unitizer instead of R. Use Q to
unitizer, as you would from
ls is masked with a specialized version for use in
In both cases you can still access the original functions by preceding them