Add tidy linting checks for buildbot_steps.yml

This commit adds tidy checks for buildbot_steps.yml, as well as unit
tests. These checks include:

* Checking buildbot_steps.yml can be parsed by a YAML loader
* buildbot_steps.yml does not contain duplicate keys
* buildbot_steps.yml keys map to a list of strings

1 files changed, 15 insertions, 0 deletions

diff --git a/python/tidy/servo_tidy_tests/test_tidy.py b/python/tidy/servo_tidy_tests/test_tidy.py
index 6dd97aee7e3..12d7b9ebae7 100644
--- a/python/tidy/servo_tidy_tests/test_tidy.py
+++ b/python/tidy/servo_tidy_tests/test_tidy.py
@@ -177,6 +177,21 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('Unordered key (found b before a)', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
+    def test_yaml_with_duplicate_key(self):
+        errors = tidy.collect_errors_for_files(iterFile('duplicate_keys_buildbot_steps.yml'), [tidy.check_yaml], [], print_text=False)
+        self.assertEqual('Duplicated Key (duplicate_yaml_key)', errors.next()[2])
+        self.assertNoMoreErrors(errors)
+
+    def test_non_list_mapped_buildbot_steps(self):
+        errors = tidy.collect_errors_for_files(iterFile('non_list_mapping_buildbot_steps.yml'), [tidy.check_yaml], [], print_text=False)
+        self.assertEqual("Key 'non-list-key' maps to type 'str', but list expected", errors.next()[2])
+        self.assertNoMoreErrors(errors)
+
+    def test_non_string_list_mapping_buildbot_steps(self):
+        errors = tidy.collect_errors_for_files(iterFile('non_string_list_buildbot_steps.yml'), [tidy.check_yaml], [], print_text=False)
+        self.assertEqual("List mapped to 'mapping_key' contains non-string element", errors.next()[2])
+        self.assertNoMoreErrors(errors)
+
     def test_lock(self):
         errors = tidy.collect_errors_for_files(iterFile('duplicated_package.lock'), [tidy.check_lock], [], print_text=False)
         msg = """duplicate versions for package "test"