Grid of individual tests

dynamic-spec.js

// if our data is more complicated and has to form things from items for example
// just pass around list of functions
const API = {
  github: (username) => 'http://github.com/' + username,
  photo: (username) => `http://github.com/${username}/avatar/`
}
const users = ['bahmutov', 'adity']
Object.keys(API).forEach((apiName) => {
  const formApiUrl = API[apiName]
  describe('api ' + apiName, () => {
    users.forEach((user) => {
      const url = formApiUrl(user)
      // assert url works
    })
  })
})

spec.js

// simple static data1 / data2 grid
function length(x) { return x.length }
function double(x) { return x + x }
const items = ['foo', 'bar', 'baz']
const actions = [length, double]
actions.forEach((action) => {
  describe(action.name, () => {
    items.forEach((item) => {
      it('is computes truthy for item ' + item, () => {
        la(action(item), 'failed action', action.name, 'for item', item)
      })
    })
  })
})

will output something like this

length
  - it computes truthy for foo
  - it computes truthy for bar
  - it computes truthy for baz
double
  - it computes truthy for foo
  - it computes truthy for bar
  - it computes truthy for baz