CLN: fixturize & split test_base
it would be nice to use our ``indices`` fixture rather than the self.indices in ``pandas/tests/test_base.py`` as this is a bit cleaner and more flexible esp with subclasses. We also might consider splitting up test_base.py to some extent by function maybe splitting up to

test_construction
test_set_ops
test_reshaping
test_indexing

would accept multiple PR's to close this.