Define a step

Provide a description that matches steps in feature files and the implementation function that will be run.

Usage

given(description, implementation)

when(description, implementation)

then(description, implementation)

Arguments

description

A description of the step.

A simple version of a Cucumber expression. The description is used by the cucumber::test function to find an implementation of a step from a feature file. The description can contain placeholders in curly braces, e.g. "I have {int} cucumbers in my basket". If no step definition is found an error will be thrown. If multiple steps definitions for a single step are found an error will be thrown. Make sure the description is unique for each step.

implementation

A function that will be run when the step is executed. The implementation function should always have the last parameter named context. It holds the environment where state should be stored to be passed to the next step.

If a step has a description "I have {int} cucumbers in my basket" then the implementation function should be a function(n_cucumbers, context). The {int} value will be passed to n_cucumbers, this parameter can have any name.

If a table or a docstring is defined for a step, it will be passed as an argument after plceholder parameters and before context. The function should be a function(n_cucumbers, table, context). See an example on how to write implementation that uses tables or docstrings.

Value

A function of class step, invisibly. Function should be called for side effects.

Details

Placeholders in expressions are replaced with regular expressions that match values in the feature file. The regular expressions are generated during runtime based on defined parameter types. The expression "I have {int} cucumbers in my basket" will be converted to "I have [+-]?(?<![.])[:digit:]+(?![.]) cucumbers in my basket". The extracted value of {int} will be passed to the implementation function after being transformed with as.integer.

To define your own parameter types use define_parameter_type.

See also

define_parameter_type()

Examples

given("I have {int} cucumbers in my basket", function(n_cucumbers, context) {
  context$n_cucumbers <- n_cucumbers
})

given("I have {int} cucumbers in my basket and a table", function(n_cucumbers, table, context) {
  context$n_cucumbers <- n_cucumbers
  context$table <- table
})

when("I eat {int} cucumbers", function(n_cucumbers, context) {
  context$n_cucumbers <- context$n_cucumbers - n_cucumbers
})

then("I should have {int} cucumbers in my basket", function(n_cucumbers, context) {
  expect_equal(context$n_cucumbers, n_cucumbers)
})