A simple behavior-driven development (BDD) domain-specific language for writing tests. The language is similar to RSpec for Ruby or Mocha for JavaScript. BDD tests read like sentences and it should thus be easier to understand what the specification of a function/component is.
Details
Tests using the describe syntax not only verify the tested code, but
also document its intended behaviour. Each describe block specifies a
larger component or function and contains a set of specifications. A
specification is defined by an it block. Each it block
functions as a test and is evaluated in its own environment. You
can also have nested describe blocks.
This test syntax helps to test the intended behaviour of your code. For
example: you want to write a new function for your package. Try to describe
the specification first using describe, before your write any code.
After that, you start to implement the tests for each specification (i.e.
the it block).
Use describe to verify that you implement the right things and use
test_that() to ensure you do the things right.
Examples
describe("matrix()", {
it("can be multiplied by a scalar", {
m1 <- matrix(1:4, 2, 2)
m2 <- m1 * 2
expect_equal(matrix(1:4 * 2, 2, 2), m2)
})
it("can have not yet tested specs")
})
#> Test passed 🥳
#> Test passed 🥇
# Nested specs:
## code
addition <- function(a, b) a + b
division <- function(a, b) a / b
## specs
describe("math library", {
describe("addition()", {
it("can add two numbers", {
expect_equal(1 + 1, addition(1, 1))
})
})
describe("division()", {
it("can divide two numbers", {
expect_equal(10 / 2, division(10, 2))
})
it("can handle division by 0") #not yet implemented
})
})
#> Test passed 🎊
#> Test passed 😸
#> Test passed 😀