add tests

tests/Test/Basic.hs

+module Test.Basic
+    ( tests
+    ) where
+
+import Test.Tasty
+import Test.Tasty.HUnit
+import Test.Utils
+import System.IO.Unsafe
+import Data.List
+
+import IGraph
+
+tests :: TestTree
+tests = testGroup "Basic tests"
+    [ graphCreation
+    ]
+
+graphCreation :: TestTree
+graphCreation = testGroup "Graph creation"
+    [ testCase "" $ assertBool "" $ nNodes simple == 3 && nEdges simple == 3
+    , testCase "" $ [(0,1),(1,2),(2,0)] @=? (sort $ edges simple)
+    , testCase "" $ assertBool "" $ nNodes gr == 100 && nEdges gr == 1000
+    , testCase "" $ edgeList @=? (sort $ edges gr)
+    ]
+  where
+    edgeList = sort $ unsafePerformIO $ randEdges 1000 100
+    gr = mkGraph (100,Nothing) (edgeList, Nothing) :: LGraph D () ()
+    simple = mkGraph (3,Nothing) ([(0,1),(1,2),(2,0)],Nothing) :: LGraph D () ()

tests/Test/Utils.hs

+module Test.Utils where
+
+import Control.Monad
+import System.Random
+import Data.List
+
+randEdges :: Int  -- ^ number of edges to generate
+          -> Int  -- ^ number of nodes in the graph
+          -> IO [(Int, Int)]
+randEdges n nd = do
+    fr <- replicateM (2*n) $ randomRIO (0,nd-1)
+    to <- replicateM (2*n) $ randomRIO (0,nd-1)
+    return $ take n $ nub $ filter (uncurry (/=)) $ zip fr to

tests/test.hs

+import qualified Test.Basic as Basic
+import Test.Tasty
+
+main :: IO ()
+main = defaultMain $ testGroup "Haskell-igraph Tests"
+    [ Basic.tests
+    ]