Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -156,8 +156,10 @@ macos_test_sdist_python38:
 
 windows_test_sdist_python38:
   <<: *test_sdist_template_defintion
-  before_script:
+  script:
     - call "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\VC\\Auxiliary\\Build\\vcvarsall.bat" amd64 -vcvars_ver=14.16
+    - pip install --pre --find-links artifacts/ --no-binary hdf5plugin hdf5plugin
+    - python -m hdf5plugin.test
   extends: .windows_base_python38