Add spinglass corrected test (clustering)

tests/Test/Algorithms.hs

@@ -144,16 +144,18 @@ bridgeTest = testCase "Bridges" $ edgeLab g <$> bridges g @?= ["bridge"]
 
 communityTest :: TestTree
 communityTest = testGroup "Community"
-    [ consistency, consistency2, consistency3]
+    [ testGroup "Consistency" [ consistency, consistency2, consistency3 ]
+    , testGroup "Correctness" [ communityCorrectnessTests ]
+    ]
   where
-    consistency = testCase "Consistency" $ do
+    consistency = testCase "spinglass" $ do
         rs <- replicateM 50 $ withSeed 134 $ findCommunity zacharyKarate Nothing Nothing spinglass
         all (== head rs) rs @=? True
-    consistency2 = testCase "Consistency -- leiden" $ do
+    consistency2 = testCase "leiden" $ do
         rs <- replicateM 50 $ withSeed 234 $ findCommunity zacharyKarate Nothing Nothing leiden
         True @=? all (== head rs) rs
 
-    consistency3 = testCase "Consistency -- infomap" $ do
+    consistency3 = testCase "infomap" $ do
         rs <- replicateM 50 $ withSeed 234 $ findCommunity zacharyKarate Nothing Nothing infomap
         True @=? all (== head rs) rs
 
@@ -162,6 +164,26 @@ communityTest = testGroup "Community"
         , (3, 4), (5, 6), (5, 7), (5, 8), (5, 9), (6, 7), (6, 8), (6, 9), (7, 8)
         , (7, 9), (8, 9), (0, 5) ] :: Graph 'U () ()
 
+communityCorrectnessTests :: TestTree
+communityCorrectnessTests = testGroup "Clustering" [
+    testCase "spinglass" spinglassClustering
+  ]
+  where
+    spinglassClustering :: Assertion
+    spinglassClustering = do
+      clusters <- withSeed 1 $ findCommunity testGraph Nothing Nothing spinglass
+      clusters @?= [[3,4], [0,1,2]]
+
+    testGraph :: Graph 'U () ()
+    testGraph = mkGraphUfromEdges [(0,1),(1,2),(2,0),(2,3),(3,4),(4,2)]
+
+-- | Helper function to create an undirected graph from undirected edges.
+mkGraphUfromEdges :: [(Int, Int)] -> Graph 'U () ()
+mkGraphUfromEdges es = mkGraph (replicate n ()) $ zip es $ repeat ()
+  where
+    (a,b) = unzip es
+    n = length (nub $ a <> b)
+
 pagerankTest :: TestTree
 pagerankTest = testGroup "PageRank"
     [ consistency