If you are using the RStudio IDE, gradethis_demo() opens an example learnr
file that demonstrates how to use the grader package to check student code.
Details
The tutorial sets the learnr exercise.checker option to
gradethis_exercise_checker() in the document's setup chunk.
It then uses three different exercise checking methods:
grade_result(), grade_conditions(), and grade_code().
To use a checking method, follow the exercise chunk with a chunk whose label
matches the label of the exercise chunk (ex: myexercise) but includes the suffix
-check (ex: myexercise-check). Call any checking method in that chunk.
To ensure that checking method can provide informative feedback,
you may provide custom correct and incorrect messages.
If you are not using RStudio IDE, you can access the demo file at
system.file("extdata", "grading-demo/grading-demo.Rmd", package = "grader").