skip test on OSX that cannot pass

because ../spack-setup.sh doesn't work on OSX (yet)

tests.py

@@ -7,6 +7,7 @@ import subprocess
 from pathlib import Path
 import logging
 import datetime
+import sys
 
 import pytest
 
@@ -186,7 +187,6 @@ def test_record_script_execution_summary(tmp_path):
         last_line = f.readlines()[-1]
         assert "Spack environments branch: dev-23a " in last_line
 
-
 def test_install_environment_wrong_toolchain(tmp_path):
     """Test exception is raised for non-existing toolchain."""
     # Expect an Exception when wrong toolchains are provided
@@ -210,6 +210,8 @@ def test_install_environment_wrong_mpsd_release(tmp_path):
         )
 
 
+@pytest.mark.skipif(sys.platform == "darwin", 
+                    reason="install not working on OSX")
 def test_install_environment_zlib():
     """Test installation of toolchain."""
     # Prepare a test installation of global generic