Lazy check estimator

[amueller]

This makes everything work as expected, I think.

from itertools import chain

import pytest
from sklearn.base import BaseEstimator
from sklearn.utils.estimator_checks import check_estimator
from sklearn.utils.estimator_checks import set_check_estimator_ids
from sklearn.linear_model import SGDClassifier
from sklearn.pipeline import Pipeline
from sklearn.feature_selection import RFE


class Bla(BaseEstimator):
    def __init__(self, a, b):
        self.a = a
        self.b = b

# first three pass, pipeline skips, last fails
estimators = [SGDClassifier(), SGDClassifier, RFE, Pipeline, Bla]


@pytest.mark.parametrize(
    'estimator, check',
    chain.from_iterable(check_estimator(est, generate_only=True)
                        for est in estimators),
    ids=set_check_estimator_ids)
def test_sklearn_compatible_estimator(estimator, check):
    check(estimator)