describe: a BDD testing language

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Description

A simple BDD DSL for writing tests. The language is similiar 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.

Usage

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describe(description, code)

Arguments

description

description of the feature

code

test code containing the specs

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 definied 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 intented 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

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describe("matrix()", {
  it("can be multiplied by a scalar", {
    m1 <- matrix(1:4, 2, 2)
    m2 <- m1 * 2
    expect_equivalent(matrix(1:4 * 2, 2, 2), m2)
  })
  it("can have not yet tested specs")
})

# 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_equivalent(1 + 1, addition(1, 1))
    })
  }) 
  describe("division()", {
    it("can divide two numbers", {
      expect_equivalent(10 / 2, division(10, 2))   
    })
    it("can handle division by 0") #not yet implemented
  })  
})

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