Commands not fully cloned during the shrinking process

[dubzzz]

Travis detected the following corner cases:

FAIL test/e2e/model/CommandsArbitrary.spec.ts (12.755s)
  ● CommandsArbitrary (seed: 1545186172739) › commands › Should shrink towards minimal case even with other arbitraries
    expect(received).toEqual(expected)
    Expected value to equal:
      "failure"
    Received:
      "success,failure"
      134 |       );
      135 |       expect(out.failed).toBe(true);
    > 136 |       expect(out.counterexample![1].toString()).toEqual('failure');
          |                                                 ^
      137 |     });
      138 |   });
      139 | });
      at Object.<anonymous> (test/e2e/model/CommandsArbitrary.spec.ts:136:49)

[dubzzz]

Current investigation proved that the issue is related to the fact that integer arbitraries memoize whenever it shrinks once to zero, after that it will not shrink to zero anymore.

√ [[7,7],,[]]
√ [[],,[2,3]]
√ [[3,6],success,success,[]]
√ [[3,8],,[8,1]]
× [[6,0,5],success,success,failure,[]]
. √ [[],,[]]
. √ [[0,5],success,success,[]]
. √ [[0,0,5],success,success,[]]
. × [[3,0,5],success,failure,[]]
. . √ [[0,5],success,success,[]]
. . × [[2,0,5],success,failure,[]]
. . . √ [[0,5],success,success,[]]
. . . × [[1,0,5],success,failure,[]]
. . . . √ [[0,5],success,success,[]]
. . . . × [[1],failure,[]]
. . . . . √ [[1],,[]]
. . . . . √ [[1],failure,[]]
. . . . . × [[1],success,failure,[]]
. . . . . . √ [[1],failure,[]]

For the moment, I see no easy fix to have it working while keeping an efficient shrinker for integers and by transitivity (all arbitraries derive from this one) all others.

[dubzzz]

PR #271 is supposed to help troubleshooting this kind of issue

[dubzzz]

The last line of the execution dump - ie √ [[1],failure,[]] - shows that failure command has been executed while the run has been considered to be a green one.

As commands highly depends on cloneable capabilities it might be related to an issue while cloning them: failure one might not have been cloned.