It is not mandatory to test all the possible outputs in fixed tests.

No test cases for [queen, bishop] solutions: example of one:

`
test case
test.assert_equals(

promotion(
  [
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', 'K', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '], 
    [' ', ' ', 'P', ' ', ' ', ' ', ' ', ' ']
  ]
), 
["queen","bishop"]

)

`