cc_resolv_conf: introduce tests and stabilise output across Python versions (#251)

This is a follow-up to #144 which fixed the rendering behaviour.

While writing the tests, CI failed due to dict iteration differences across Python versions, so this also sorts output so that we will produce the same output across Python versions.

2 files changed, 87 insertions, 1 deletions

diff --git a/cloudinit/config/tests/test_resolv_conf.py b/cloudinit/config/tests/test_resolv_conf.py
new file mode 100644
index 00000000..f3d97b82
--- /dev/null
+++ b/cloudinit/config/tests/test_resolv_conf.py
@@ -0,0 +1,86 @@
+from unittest import mock
+
+import pytest
+
+from cloudinit.config.cc_resolv_conf import generate_resolv_conf
+
+
+EXPECTED_HEADER = """\
+# Your system has been configured with 'manage-resolv-conf' set to true.
+# As a result, cloud-init has written this file with configuration data
+# that it has been provided. Cloud-init, by default, will write this file
+# a single time (PER_ONCE).
+#\n\n"""
+
+
+class TestGenerateResolvConf:
+    @mock.patch("cloudinit.config.cc_resolv_conf.templater.render_to_file")
+    def test_default_target_fname_is_etc_resolvconf(self, m_render_to_file):
+        generate_resolv_conf("templates/resolv.conf.tmpl", mock.MagicMock())
+
+        assert [
+            mock.call(mock.ANY, "/etc/resolv.conf", mock.ANY)
+        ] == m_render_to_file.call_args_list
+
+    @mock.patch("cloudinit.config.cc_resolv_conf.templater.render_to_file")
+    def test_target_fname_is_used_if_passed(self, m_render_to_file):
+        generate_resolv_conf(
+            "templates/resolv.conf.tmpl", mock.MagicMock(), "/use/this/path"
+        )
+
+        assert [
+            mock.call(mock.ANY, "/use/this/path", mock.ANY)
+        ] == m_render_to_file.call_args_list
+
+    # Patch in templater so we can assert on the actual generated content
+    @mock.patch("cloudinit.templater.util.write_file")
+    # Parameterise with the value to be passed to generate_resolv_conf as the
+    # `params` parameter, and a list of the expected lines after the header as
+    # `extra_lines`.
+    @pytest.mark.parametrize(
+        "params,expected_extra_line",
+        [
+            # No options
+            ({}, None),
+            # Just a true flag
+            ({"options": {"foo": True}}, "options foo"),
+            # Just a false flag
+            ({"options": {"foo": False}}, None),
+            # Just an option
+            ({"options": {"foo": "some_value"}}, "options foo:some_value"),
+            # A true flag and an option
+            (
+                {"options": {"foo": "some_value", "bar": True}},
+                "options bar foo:some_value",
+            ),
+            # Two options
+            (
+                {"options": {"foo": "some_value", "bar": "other_value"}},
+                "options bar:other_value foo:some_value",
+            ),
+            # Everything
+            (
+                {
+                    "options": {
+                        "foo": "some_value",
+                        "bar": "other_value",
+                        "baz": False,
+                        "spam": True,
+                    }
+                },
+                "options spam bar:other_value foo:some_value",
+            ),
+        ],
+    )
+    def test_flags_and_options(
+        self, m_write_file, params, expected_extra_line
+    ):
+        generate_resolv_conf("templates/resolv.conf.tmpl", params)
+
+        expected_content = EXPECTED_HEADER
+        if expected_extra_line is not None:
+            # If we have any extra lines, expect a trailing newline
+            expected_content += "\n".join([expected_extra_line, ""])
+        assert [
+            mock.call(mock.ANY, expected_content, mode=mock.ANY)
+        ] == m_write_file.call_args_list
diff --git a/templates/resolv.conf.tmpl b/templates/resolv.conf.tmpl
index b6d46b4b..f870be67 100644
--- a/templates/resolv.conf.tmpl
+++ b/templates/resolv.conf.tmpl
@@ -32,7 +32,7 @@ options
  {{flag-}}
 {% endfor %}
 
-{%- for key, value in options.items() %}
+{%- for key, value in options.items()|sort %}
  {{key}}:{{value-}}
 {% endfor %}
 {% endif %}