Merge #2537

2537: Fix massive memory leak in unit tests r=Anviking a=Anviking

# Issue Number

ADP-758, #2472 

# Overview

- [x] Make sure to also close the DBLayers we create!
- [x] <s>Use validateGenerator to also test non-QSM Arbitrary instances</s>
- [ ] <s>TODO: Look a bit more at the generators / validation of them, could perhaps split the PR too.</s>

# Comments

Before this fix the memory usage would steadily climb upwards 5-15GB. Now it's at most ~40 MB.

### Running part of unit tests before fix:
<img width="1167" alt="ska__rmavbild_2021-02-25_kl _12 34 43" src="https://user-images.githubusercontent.com/304423/109172195-cafd8c00-7782-11eb-8afd-a40732fccded.png">


### Running all unit tests after fix:
<img width="1399" alt="Skärmavbild 2021-02-25 kl  15 54 16" src="https://user-images.githubusercontent.com/304423/109171975-938edf80-7782-11eb-904b-9404708fbdde.png">


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Co-authored-by: Johannes Lund <[email protected]>

lib/core/test/unit/Cardano/Pool/DB/SqliteSpec.hs

@@ -14,51 +14,42 @@ module Cardano.Pool.DB.SqliteSpec
 import Prelude
 
 import Cardano.BM.Trace
-    ( traceInTVarIO )
+    ( nullTracer )
 import Cardano.DB.Sqlite
-    ( DBLog (..), SqliteContext )
+    ( DBLog (..) )
 import Cardano.Pool.DB
     ( DBLayer (..) )
 import Cardano.Pool.DB.Log
     ( PoolDbLog (..) )
 import Cardano.Pool.DB.Properties
     ( properties )
 import Cardano.Pool.DB.Sqlite
-    ( newDBLayer, withDBLayer )
+    ( withDBLayer )
 import Cardano.Wallet.DummyTarget.Primitive.Types
     ( dummyTimeInterpreter )
 import System.Directory
     ( copyFile )
 import System.FilePath
     ( (</>) )
 import Test.Hspec
-    ( Spec, before, describe, it, shouldBe )
+    ( Spec, around, describe, it, shouldBe )
 import Test.Hspec.Extra
     ( parallel )
 import Test.Utils.Paths
     ( getTestData )
 import Test.Utils.Trace
     ( captureLogging )
-import UnliftIO.STM
-    ( TVar, newTVarIO )
 import UnliftIO.Temporary
     ( withSystemTempDirectory )
 
--- | Set up a DBLayer for testing, with the command context, and the logging
--- variable.
-newMemoryDBLayer :: IO (DBLayer IO)
-newMemoryDBLayer = snd . snd <$> newMemoryDBLayer'
-
-newMemoryDBLayer' :: IO (TVar [PoolDbLog], (SqliteContext, DBLayer IO))
-newMemoryDBLayer' = do
-    logVar <- newTVarIO []
-    (logVar, ) <$> newDBLayer (traceInTVarIO logVar) Nothing ti
-  where
-    ti = dummyTimeInterpreter
+withMemoryDBLayer
+    :: (DBLayer IO -> IO a)
+    -> IO a
+withMemoryDBLayer = withDBLayer nullTracer Nothing dummyTimeInterpreter
 
 spec :: Spec
 spec = parallel $ do
-    before newMemoryDBLayer $ do
+    around withMemoryDBLayer $ do
         parallel $ describe "Sqlite" properties
 
     describe "Migration Regressions" $ do