tests: Disallow use of util.subp except for where needed.

In many cases, cloud-init uses 'util.subp' to run a subprocess.
This is not really desirable in our unit tests as it makes the tests
dependent upon existance of those utilities.

The change here is to modify the base test case class (CiTestCase) to
raise exception any time subp is called.  Then, fix all callers.
For cases where subp is necessary or actually desired, we can use it
via
  a.) context hander CiTestCase.allow_subp(value)
  b.) class level self.allowed_subp = value

Both cases the value is a list of acceptable executable names that
will be called (essentially argv[0]).

Some cleanups in AltCloud were done as the code was being updated.

1 files changed, 13 insertions, 5 deletions

diff --git a/tests/unittests/test_handler/test_handler_chef.py b/tests/unittests/test_handler/test_handler_chef.py
index f4bbd66d..b16532ea 100644
--- a/tests/unittests/test_handler/test_handler_chef.py
+++ b/tests/unittests/test_handler/test_handler_chef.py
@@ -36,13 +36,21 @@ class TestInstallChefOmnibus(HttprettyTestCase):
 
     @mock.patch("cloudinit.config.cc_chef.OMNIBUS_URL", OMNIBUS_URL_HTTP)
     def test_install_chef_from_omnibus_runs_chef_url_content(self):
-        """install_chef_from_omnibus runs downloaded OMNIBUS_URL as script."""
-        chef_outfile = self.tmp_path('chef.out', self.new_root)
-        response = '#!/bin/bash\necho "Hi Mom" > {0}'.format(chef_outfile)
+        """install_chef_from_omnibus calls subp_blob_in_tempfile."""
+        response = b'#!/bin/bash\necho "Hi Mom"'
         httpretty.register_uri(
             httpretty.GET, cc_chef.OMNIBUS_URL, body=response, status=200)
-        cc_chef.install_chef_from_omnibus()
-        self.assertEqual('Hi Mom\n', util.load_file(chef_outfile))
+        ret = (None, None)  # stdout, stderr but capture=False
+
+        with mock.patch("cloudinit.config.cc_chef.util.subp_blob_in_tempfile",
+                        return_value=ret) as m_subp_blob:
+            cc_chef.install_chef_from_omnibus()
+        # admittedly whitebox, but assuming subp_blob_in_tempfile works
+        # this should be fine.
+        self.assertEqual(
+            [mock.call(blob=response, args=[], basename='chef-omnibus-install',
+                       capture=False)],
+            m_subp_blob.call_args_list)
 
     @mock.patch('cloudinit.config.cc_chef.url_helper.readurl')
     @mock.patch('cloudinit.config.cc_chef.util.subp_blob_in_tempfile')