Create a genInstanceMaybeBiggerThan function

This is used only once when testing Cluster.hs, but having it abstracted
clarifies there what that call is about, makes that test shorter, and
allows us to better do refactoring of the main genInstanceSmallerThan
generator.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

htest/Test/Ganeti/HTools/Cluster.hs

@@ -37,7 +37,7 @@ import Test.Ganeti.TestHelper
 import Test.Ganeti.TestCommon
 import Test.Ganeti.TestHTools
 import Test.Ganeti.HTools.Instance ( genInstanceSmallerThanNode
-                                   , genInstanceSmallerThan )
+                                   , genInstanceMaybeBiggerThanNode )
 import Test.Ganeti.HTools.Node (genOnlineNode, genNode)
 
 import Ganeti.BasicTypes
@@ -191,10 +191,7 @@ prop_CanTieredAlloc :: Property
 prop_CanTieredAlloc =
   forAll (choose (2, 5)) $ \count ->
   forAll (genOnlineNode `suchThat` isNodeBig 4) $ \node ->
-  forAll (genInstanceSmallerThan
-            (Node.availMem  node + Types.unitMem * 2)
-            (Node.availDisk node + Types.unitDsk * 3)
-            (Node.availCpu  node + Types.unitCpu * 4)) $ \inst ->
+  forAll (genInstanceMaybeBiggerThanNode node) $ \inst ->
   let nl = makeSmallCluster node count
       il = Container.empty
       rqnodes = Instance.requiredNodes $ Instance.diskTemplate inst

htest/Test/Ganeti/HTools/Instance.hs

@@ -29,6 +29,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 module Test.Ganeti.HTools.Instance
   ( testHTools_Instance
   , genInstanceSmallerThanNode
+  , genInstanceMaybeBiggerThanNode
   , genInstanceSmallerThan
   , Instance.Instance(..)
   ) where
@@ -66,6 +67,13 @@ genInstanceSmallerThanNode node =
                          (Node.availDisk node `div` 2)
                          (Node.availCpu node `div` 2)
 
+-- | Generates an instance possibly bigger than a node.
+genInstanceMaybeBiggerThanNode :: Node.Node -> Gen Instance.Instance
+genInstanceMaybeBiggerThanNode node =
+  genInstanceSmallerThan (Node.availMem  node + Types.unitMem * 2)
+                         (Node.availDisk node + Types.unitDsk * 3)
+                         (Node.availCpu  node + Types.unitCpu * 4)
+
 -- let's generate a random instance
 instance Arbitrary Instance.Instance where
   arbitrary = genInstanceSmallerThan maxMem maxDsk maxCpu