Unit-Testing

[pfistfl]

Without having looked through all the PR's it would be cool to have unit-tests wrt the following criteria:

• Test that results from functions are as expected:
  • Do not just test whether class fits, but that content makes sense as well for example:
  • task$data() returns the expected variable types / column names / row order
  • predictions match the data, no row-shuffling occurs
• Test all allowed and not-allowed edge-cases: What happens for one-row / two-row / one-column / multiple-columns / with or without exogeneous variables?
  • Do I get a meaningful error in cases where a learner can not deal with some feature type?
  • Do the resampling methods create meaningful methods or errors for one-row tasks etc.

[corneliagru]

mostly implemented in #56 and in #57