From daceac95fc6c997c3322734446f1631ca16a258e Mon Sep 17 00:00:00 2001
From: Wolfgang Witt <Wolfgang.Witt@campus.lmu.de>
Date: Wed, 24 Feb 2021 16:33:01 +0100
Subject: [PATCH] chore(test): relax requirements for justified nullResult

Instances with bigger user buckets than the smallest room might correctly fail
Thus, don't report an error for them.
---
 src/Handler/Utils/Exam.hs      |  2 +-
 test/Handler/Utils/ExamSpec.hs | 24 ++++++++++++++++--------
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/Handler/Utils/Exam.hs b/src/Handler/Utils/Exam.hs
index 874b8144b..b54ac379c 100644
--- a/src/Handler/Utils/Exam.hs
+++ b/src/Handler/Utils/Exam.hs
@@ -636,7 +636,7 @@ examAutoOccurrence (hash -> seed) rule ExamAutoOccurrenceConfig{..} occurrences
                         withAlphabetChars :: [CI Char] -> [CI Char]
                         withAlphabetChars [] = []
                         withAlphabetChars (c:cs)
-                          | elem c alphabet = c : withAlphabetChars cs
+                          | c `elem` alphabet = c : withAlphabetChars cs
                           | otherwise= case previousAlphabetChar c of
                             Nothing -> []
                             (Just c') -> c' : replicate (length cs) (last alphabet)
diff --git a/test/Handler/Utils/ExamSpec.hs b/test/Handler/Utils/ExamSpec.hs
index 0bf308ba0..c2c3b673f 100644
--- a/test/Handler/Utils/ExamSpec.hs
+++ b/test/Handler/Utils/ExamSpec.hs
@@ -316,16 +316,24 @@ spec = do
         mappingImpossible
             rule
             userProperties@(sort . map (ruleProperty rule . fst) . Map.elems . Map.filter (isRelevantUser rule) -> relevantUsers)
-            (map snd . Map.toList . adjustOccurrences userProperties -> occurrences') = go relevantUsers occurrences'
+            (map snd . Map.toList . adjustOccurrences userProperties -> occurrences') = go 0 True relevantUsers occurrences'
             where
-                go :: [Maybe Text] -> [Natural] -> Bool
-                go [] _occurrences = False
-                go _remainingUsers [] = True
-                go remainingUsers (0:t) = go remainingUsers t
-                go remainingUsers@(h:_t) (firstOccurrence:laterOccurrences)
-                    | nextUsers <= firstOccurrence = go remainingUsers' $ firstOccurrence - nextUsers : laterOccurrences
-                    | otherwise = go remainingUsers laterOccurrences
+                smallestRoom :: Natural
+                smallestRoom = maybe 0 minimum $ fromNullable occurrences'
+                -- If there exists a bucket with the same tag bigger than the smallest room a nullResult might be returned
+                -- It may still work, but is not guaranteed (e.g. both the first bucket)
+                go :: Natural -> [Maybe Text] -> [Natural] -> Bool
+                go biggestUserBucket [] _occurrences = biggestUserBucket > small
+                go _biggestUserBucket _remainingUsers [] = True
+                go biggestUserBucket remainingUsers (0:t) = go biggestUserBucket remainingUsers t
+                go biggestUserBucket remainingUsers@(h:_t) (firstOccurrence:laterOccurrences)
+                    | nextUsers <= firstOccurrence
+                    = go (max biggestUserBucket nextUsers) remainingUsers' $ firstOccurrence - nextUsers : laterOccurrences
+                    | otherwise
+                    = go biggestUserBucket remainingUsers laterOccurrences
                     where
+                        nextUsers :: Natural
+                        remainingUsers' :: [Maybe Text]
                         (fromIntegral . length -> nextUsers, remainingUsers') = span (== h) remainingUsers
         ruleProperty :: ExamOccurrenceRule -> UserProperties -> Maybe Text
         ruleProperty rule = case rule of