py.test dask --runslow 
============================= test session starts ==============================
platform linux -- Python 3.7.9, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /home/runner/work/dask/dask, configfile: setup.cfg
plugins: forked-1.3.0, xdist-2.2.1
collected 757 items / 1 error / 8 skipped / 748 selected

==================================== ERRORS ====================================
____________ ERROR collecting dask/tests/test_graph_manipulation.py ____________
ImportError while importing test module '/home/runner/work/dask/dask/dask/tests/test_graph_manipulation.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
dask/array/__init__.py:2: in <module>
    from .blockwise import blockwise, atop
dask/array/blockwise.py:9: in <module>
    from ..blockwise import blockwise as core_blockwise
dask/blockwise.py:4: in <module>
    import numpy as np
E   ModuleNotFoundError: No module named 'numpy'

The above exception was the direct cause of the following exception:
/usr/share/miniconda3/envs/test-environment/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
dask/tests/test_graph_manipulation.py:10: in <module>
    from dask.graph_manipulation import bind, checkpoint, chunks, clone, wait_on
dask/graph_manipulation.py:8: in <module>
    from .array import Array
dask/array/__init__.py:253: in <module>
    raise ImportError(str(e) + "\n\n" + msg) from e
E   ImportError: No module named 'numpy'
E   
E   Dask array requirements are not installed.
E   
E   Please either conda or pip install as follows:
E   
E     conda install dask                 # either conda install
E     python -m pip install "dask[array]" --upgrade  # or python -m pip install