diff -r 6a0b43a5dec0 -r d2b277cb948e tests/category.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/category.py	Mon Jun 24 10:13:13 2019 +0300
@@ -0,0 +1,53 @@
+from testsuite import problem_type, report_problem
+import linetypes
+from librarystandards import library_standards
+
+@problem_type('bad-category',
+    severity = 'hold',
+    message = lambda category: str.format(
+        '"{category}" is not an official category',
+        category = category,
+    )
+)
+@problem_type('bad-category-in-description',
+    severity = 'hold',
+    message = lambda category: str.format(
+        'the category "{category}" must be set using !CATEGORY '
+        'and not by description',
+        category = category,
+    )
+)
+def category_test(model):
+    if model.header.valid:
+        categories = library_standards['categories']
+        illegal_categories_in_description = [
+            category_name.lower()
+            for category_name in categories.keys()
+            if ' ' in category_name
+        ]
+        has_bad_category = False
+        if model.header.effective_category not in categories.keys():
+            try:
+                bad_object = model.find_first_header_object('category')
+            except KeyError:
+                # category was not specified using !CATEGORY, blame
+                # the description instead
+                bad_object = model.body[0]
+            has_bad_category = True
+            yield report_problem(
+                'bad-category',
+                bad_object = bad_object,
+                category = model.header.effective_category,
+            )
+        # Check if the description sets a multi-word category
+        if not has_bad_category and model.header.category is None:
+            for category_name in illegal_categories_in_description:
+                if model.header.description.lower().startswith(category_name):
+                    yield report_problem(
+                        'bad-category-in-description',
+                        bad_object = model.body[0],
+                        category = category_name.title(),
+                    )
+                    break
+
+manifest = {'tests': [category_test]}