split one test into three

(I am trying to debug the third one on the Mac, and this makes it easier.)

tests.py

@@ -147,20 +147,19 @@ def test_setup_log_cmd(tmp_path):
         assert "Spack environments branch: dev-23a " in last_line
 
 
-def test_install_environment(tmp_path):
-    """Test the installation of a toolchain.
-
-    This is a long test, its handy to test this with print statements printed to
-    stdout, use:
-      pytest -s
-    Expect an Exception when wrong toolchains are provided
-    """
+def test_install_environment_wrong_toolchain(tmp_path):
+    """Test exception is raised for non-existing toolchain."""
+    # Expect an Exception when wrong toolchains are provided
     with pytest.raises(Exception):
         mod.install_environment(
             mpsd_release="dev-23a",
             toolchains=["wrong-toolchain"],
             script_dir=(tmp_path),
         )
+
+
+def test_install_environment_wrong_mpsd_release(tmp_path):
+    """Test exception is raised for non-existing mpsd release."""
     # Expect an Exception when wrong mpsd_release is provided (part of
     # prepare_environment)
     with pytest.raises(Exception):
@@ -169,11 +168,18 @@ def test_install_environment(tmp_path):
             toolchains=["foss2021a-mpi"],
             script_dir=(tmp_path),
         )
-    # prepare a test of global generic with only zlib to test the installation
-    # prepare dev-23a release
-    # script_dir = tmp_path / "test_global_generic"
-    # for actaual installation avoid tmp_path as the lenght of the path is too long
-    # and spack complains
+
+
+def test_install_environment_zlib():
+    """Test installation of toolchain."""
+    # Prepare a test installation of global generic
+    # with only zlib to test the installation
+    # This is a long test,
+    # its handy to test this with print statements printed to
+    # stdout, use:
+    #   pytest -s
+    # for this installation avoid tmp_path as
+    # the length of the path becomes too long and spack complains
     script_dir = Path("/tmp/test_global_generic")
     if script_dir.exists():
         shutil.rmtree(script_dir)