Try and simplify MWE

tox.ini

@@ -24,38 +24,17 @@ passenv =
 setenv =
     osxclang: CC=clang-10
     linuxgcc: CC=x86_64-conda-linux-gnu-gcc
-changedir =
-    .tmp/{envname}
-description =
-    run tests with pytest
-deps =
-    :NRAO:casadata
-    glue-core
-    oldestdeps: astropy==4.0.*
-    oldestdeps: numpy==1.17.*
-    oldestdeps: dask[array]==2.0.*
-    devdeps: :NUMPY_NIGHTLY:numpy
-    devdeps: pyerfa
-    devdeps: PyYAML
-    devdeps: :ASTROPY_NIGHTLY:astropy
-    casa-oldestdeps: :NRAO:casatools==6.0.0.27
-    # Note that it looks like there is a casatools bug in 6.4.3.8
-    # https://github.com/radio-astro-tools/casa-formats-io/issues/39
-    casa-!oldestdeps: :NRAO:casatools<6.4.3.8
 conda_deps =
     osxclang: clang_osx-64==10
     osxclang: llvm-openmp
     linuxgcc: gcc_linux-64
 conda_channels =
     linuxgcc: conda-forge
-extras =
-    test
 commands =
     python --version
     pip freeze
     osxclang: conda list
-    pytest --open-files --pyargs casa_formats_io {toxinidir}/docs --cov casa_formats_io --cov-config={toxinidir}/setup.cfg {posargs}
-    coverage xml -o {toxinidir}/coverage.xml
+    pip install .
 
 [testenv:build_docs]
 changedir =