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 %}