diff --git a/tools/linter_lib/custom_check.py b/tools/linter_lib/custom_check.py
index 52f3da6384..58fd746b6a 100644
--- a/tools/linter_lib/custom_check.py
+++ b/tools/linter_lib/custom_check.py
@@ -190,9 +190,13 @@ def build_custom_checkers(by_lang):
     ]) + whitespace_rules
     python_rules = cast(RuleList, [
         {'pattern': '^(?!#)@login_required',
-         'description': '@login_required is unsupported; use @zulip_login_required'},
+         'description': '@login_required is unsupported; use @zulip_login_required',
+         'good_lines': ['@zulip_login_required', '# foo @login_required'],
+         'bad_lines': ['@login_required', ' @login_required']},
         {'pattern': '".*"%\(.*\)?$',
-         'description': 'Missing space around "%"'},
+         'description': 'Missing space around "%"',
+         'good_lines': ['"%s" % ("foo")', '"%s" % (foo)'],
+         'bad_lines': ['"%s"%("foo")', '"%s"%(foo)']},
         {'pattern': "'.*'%\(.*\)?$",
          'exclude': set(['analytics/lib/counts.py',
                          'analytics/tests/test_counts.py',
@@ -205,23 +209,39 @@ def build_custom_checkers(by_lang):
              ('static/templates/settings/bot-settings.handlebars',
               "'https://hostname.example.com/bots/followup'"),
          ]),
-         'description': 'Missing space around "%"'},
+         'description': 'Missing space around "%"',
+         'good_lines': ["'%s' % ('foo')", "'%s' % (foo)"],
+         'bad_lines': ["'%s'%('foo')", "'%s'%(foo)"]},
         # This rule is constructed with + to avoid triggering on itself
         {'pattern': " =" + '[^ =>~"]',
-         'description': 'Missing whitespace after "="'},
+         'description': 'Missing whitespace after "="',
+         'good_lines': ['a = b', '5 == 6'],
+         'bad_lines': ['a =b', 'asdf =42']},
         {'pattern': '":\w[^"]*$',
-         'description': 'Missing whitespace after ":"'},
+         'description': 'Missing whitespace after ":"',
+         'good_lines': ['"foo": bar', '"some:string:with:colons"'],
+         'bad_lines': ['"foo":bar', '"foo":1']},
         {'pattern': "':\w[^']*$",
-         'description': 'Missing whitespace after ":"'},
+         'description': 'Missing whitespace after ":"',
+         'good_lines': ["'foo': bar", "'some:string:with:colons'"],
+         'bad_lines': ["'foo':bar", "'foo':1"]},
         {'pattern': "^\s+#\w",
          'strip': '\n',
-         'description': 'Missing whitespace after "#"'},
+         'description': 'Missing whitespace after "#"',
+         'good_lines': ['a = b # some operation', '1+2 #  3 is the result'],
+         'bad_lines': [' #some operation', '  #not valid!!!']},
         {'pattern': "assertEquals[(]",
-         'description': 'Use assertEqual, not assertEquals (which is deprecated).'},
+         'description': 'Use assertEqual, not assertEquals (which is deprecated).',
+         'good_lines': ['assertEqual(1, 2)'],
+         'bad_lines': ['assertEquals(1, 2)']},
         {'pattern': "== None",
-         'description': 'Use `is None` to check whether something is None'},
+         'description': 'Use `is None` to check whether something is None',
+         'good_lines': ['if foo is None'],
+         'bad_lines': ['foo == None']},
         {'pattern': "type:[(]",
-         'description': 'Missing whitespace after ":" in type annotation'},
+         'description': 'Missing whitespace after ":" in type annotation',
+         'good_lines': ['# type: (Any, Any)', 'colon:separated:string:containing:type:as:keyword'],
+         'bad_lines': ['# type:(Any, Any)']},
         {'pattern': "type: ignore$",
          'exclude': set(['tools/tests',
                          'zerver/lib/test_runner.py',