function getCharacterThangTypeSlugTest (selector, side, data, characterProperty) {
  describe(`${side}`, () => {
    it('returns undefined when passed nothing', () => {
      expect(selector(undefined)).toBeUndefined()
    })

    it('returns undefined if the left thangType doesn\'t have type', () => {
      for (const testData of data) {
        expect(selector(testData)).toBeUndefined()
      }
    })
  })
}
This data can be used to check that none of the selectors that match
the left or right character work.
Intentionally invalid data.