     [{a: 3, b: 4}, {a: 3, b: 5}]
   ]
 ,
-  on: {'a': 'a'}
-  left: ({a: i, b: i + 1} for i in [1..3]).concat {a: null, b: 5}
-  right: ({a: i, b: i + 2} for i in [1..3]).concat {a: null, b: 6}, {a: null, b: 7}
+  on: 'a'
+  left: BASE_LEFT.concat {a: null, b: 5}
+  right: BASE_RIGHT.concat {a: null, b: 6}, {a: null, b: 7}
   expected: [
     [{a: null, b: 5}, null]
     [null, {a: null, b: 6}]

  ]
,
  on: 'a'
  left: ({a: i, b: i + 1} for i in [1..3]).concat {a: null, b: 5}
  right: ({a: i, b: i + 2} for i in [1..3]).concat {a: null, b: 6}
  expected: [
    [{a: null, b: 5}, null]
    [null, {a: null, b: 6}]

    [null, {a: 2, b: 4}]
    [null, {a: 3, b: 5}]
  ]
,
  on: 'a'
  left: BASE_LEFT.concat {a: '', b: 5}
  right: BASE_RIGHT.concat {a: '', b: 6}
  expected: [
    [{a: 1, b: 2}, {a: 1, b: 3}]
    [{a: 2, b: 3}, {a: 2, b: 4}]
