diff --git a/checks/UsageCheckTest.hs b/checks/UsageCheckTest.hs
index a10e543..e5aa478 100644
--- a/checks/UsageCheckTest.hs
+++ b/checks/UsageCheckTest.hs
@@ -184,69 +184,37 @@ testInitVar = TestList
             ,oX *:= oZ
           ]
       ]]]
- 
-   -- Single node, x not touched
-  ,testInitVarPass 0 [(0,[],[])] [] 0 0 "x"
-   -- Single node, x written to
-  ,testInitVarPass 1 [(0,[],[variable "x"])] [] 0 0 "x"
-   -- Single node, x read from (FAIL)
-  ,testInitVarFail 2 [(0,[variable "x"],[])] [] 0 0 "x"
-   -- Single node, x read from and written to (FAIL - x must be written to before the read.  
-   --   This line is akin to x = x + 1, so x must be written to beforehand)
-  ,testInitVarFail 3 [(0,[variable "x"],[variable "x"])] [] 0 0 "x"
-
-  -- Two nodes, x written to then read
-  ,testInitVarPass 10 [(0,[],[variable "x"]), (1,[variable "x"],[])] [(0,1,ESeq Nothing)] 0 1 "x"
-  -- Two nodes, x read then written to (FAIL)
-  ,testInitVarFail 11 [(0,[],[variable "x"]), (1,[variable "x"],[])] [(1,0,ESeq Nothing)] 1 0 "x"
-  -- As test 10 (x written to then read) but using the par edges.
-  ,testInitVarPass 13 [(0,[],[variable "x"]), (1,[variable "x"],[])] [(0,1,EStartPar 0)] 0 1 "x"
-  ,testInitVarPass 14 [(0,[],[variable "x"]), (1,[variable "x"],[])] [(0,1,EEndPar 0)] 0 1 "x"
-
-  -- Diamond tests (0 branches to 1 and 2, which both merge to 3):
-  -- x written to in 0 and 1, then read in 3
-  ,testInitVarPass 20 [(0,[],[]),(1,[],[variable "x"]), (2,[],[variable "x"]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- x written to only in 2 then read in 3 (FAIL)
-  ,testInitVarFail 21 [(0,[],[]),(1,[],[]), (2,[],[variable "x"]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- x definitely written to in 2, but not 1 (FAIL)
-  ,testInitVarFail 22 [(0,[],[]),(1,[],[]), (2,[],[variable "x"]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- like test 21, but the link missing from 1 to 3, so test will pass
-  ,testInitVarPass 23 [(0,[],[]),(1,[],[]), (2,[],[variable "x"]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- variable written to in 0, read in 3
-  ,testInitVarPass 24 [(0,[],[variable "x"]),(1,[],[]), (2,[],[]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- variable never written to, but read in 3
-  ,testInitVarFail 25 [(0,[],[]),(1,[],[]), (2,[],[]), (3,[variable "x"],[])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-  -- variable written to in 2 and 3, but read in 1 (FAIL):
-  ,testInitVarFail 26 [(0,[],[]),(1,[variable "x"],[]), (2,[],[variable "x"]), (3,[],[variable "x"])]
-    [(0,1,ESeq Nothing),(0,2,ESeq Nothing),(1,3,ESeq Nothing),(2,3,ESeq Nothing)] 0 3 "x"
-
-  -- Test parallel diamonds:
-  -- written to in 1 and 2, read in 3
-  -- This would fail CREW, but that's not what we're testing here:
-  ,testInitVarPass 30 [(0,[],[]),(1,[],[variable "x"]), (2,[],[variable "x"]), (3,[variable "x"],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
-  -- written to in 1, read in 3
-  ,testInitVarPass 31 [(0,[],[]),(1,[],[variable "x"]), (2,[],[]), (3,[variable "x"],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
-  -- written to in 0, read in 3
-  ,testInitVarPass 32 [(0,[],[variable "x"]),(1,[],[]), (2,[],[]), (3,[variable "x"],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
-  -- never written to, but read in 3:
-  ,testInitVarFail 33 [(0,[],[]),(1,[],[]), (2,[],[]), (3,[variable "x"],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
-  -- written to in 1, read in 2 (again, would fail CREW) (FAIL):
-  ,testInitVarFail 34 [(0,[],[]),(1,[],[variable "x"]), (2,[variable "x"],[]), (3,[],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
-  -- written to in 1, read in 2 and 3 (again, would fail CREW) (FAIL):
-  ,testInitVarFail 35 [(0,[],[]),(1,[],[variable "x"]), (2,[variable "x"],[]), (3,[variable "x"],[])]
-    [(0,1,EStartPar 0),(0,2,EStartPar 0),(1,3,EEndPar 0),(2,3,EEndPar 0)] 0 3 "x"
 
+  ,test "Written to in all (two) IF guards, then self-assign" $ wrap $
+    oSEQ [
+      decl (return A.Int) oX [
+        oIF [
+          ifChoice (False, oX *:= return (3::Int))
+          ,ifChoice (False, oX *:= return (4::Int))
+        ]
+      ]
+      ,oX *:= oX
+    ]
+  ,testWarn "Written to in only one IF guards, then self-assign" $ wrap $
+    oSEQ [
+      decl (return A.Int) oX [
+        oIF [
+          ifChoice (False, oX *:= return (3::Int))
+          ,ifChoice (False, oSKIP)
+        ]
+      ]
+      ,oX *:= oX
+    ]
+  ,testWarn "Read from in last IF guards, then self-assign" $ wrap $
+    oSEQ [
+      decl (return A.Int) oX [
+        oIF [
+          ifChoice (False, oX *:= return (3::Int))
+          ,ifChoice (oX, oX *:= return (4::Int))
+        ]
+      ]
+      ,oX *:= oX
+    ]
 
   -- Test loops (0 -> 1, 1 -> 2 -> 3 -> 1, 1 -> 4)
   -- Loop, nothing happens:
diff --git a/common/OccamEDSL.hs b/common/OccamEDSL.hs
index 5f716c2..dab7842 100644
--- a/common/OccamEDSL.hs
+++ b/common/OccamEDSL.hs
@@ -17,13 +17,15 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 -}
 
 -- | The necessary components for using an occam EDSL (for building test-cases).
-module OccamEDSL (ExpInp, ExpInpT, oSEQ, oPAR, oPROC, oSKIP, oINT,
-  oCASE, oCASEinput, oALT, guard,
+module OccamEDSL (ExpInp, ExpInpT,
+  oSEQ, oPAR, oPROC, oSKIP, oINT,
+  oCASE, oCASEinput, caseOption, inputCaseOption, 
+  oALT, guard,
+  oIF, ifChoice,
   Occ, oA, oB, oC, oX, oY, oZ, p0, p1, p2, (*?), (*!), (*:=), (*+), decl, decl', decl'',
     oempty, testOccamPass,
     oprocess,
     testOccamPassWarn, testOccamPassTransform, ExpInpC(shouldComeFrom),
-    caseOption, inputCaseOption, 
     becomes) where
 
 import Control.Monad.State hiding (guard)
@@ -168,6 +170,15 @@ instance Castable (A.Structured A.Variant) A.Variant where
   makeStruct = id
   makePlain = A.Only emptyMeta
 
+instance Castable A.Choice A.Choice where
+  makeStruct = A.Only emptyMeta
+  makePlain = id
+
+instance Castable (A.Structured A.Choice) A.Choice where
+  makeStruct = id
+  makePlain = A.Only emptyMeta
+
+
 p0, p1, p2 :: Castable c A.Process => O c
 p0 = return $ makePlain $ A.Skip emptyMeta
 p1 = return $ makePlain $ A.Seq emptyMeta (A.Several emptyMeta [])
@@ -209,6 +220,15 @@ guard (inp, body)
        body' <- body
        return $ A.Only emptyMeta $ A.Alternative m (A.True emptyMeta) v im body'
 
+oIF :: Castable c A.Process => [O (A.Structured A.Choice)] -> O c
+oIF = liftM (makePlain . A.If emptyMeta . singlify . A.Several emptyMeta) . sequence
+
+ifChoice :: (CanBeExpression e, Castable c A.Choice) => (e, O A.Process) -> O c
+ifChoice (e, body)
+  = do e' <- liftExpInp $ expr e
+       body' <- body
+       return $ makePlain $ A.Choice emptyMeta e' body'
+
 singlify :: Data a => A.Structured a -> A.Structured a
 singlify (A.Several _ [s]) = s
 singlify ss = ss
@@ -246,17 +266,15 @@ oZ = return $ variable "Z"
   dest <- liftExpInp bdest >>* inputItem
   return $ makePlain $ A.Input emptyMeta ch dest
 
-(*!), (*:=) :: CanBeExpression e => ExpInp A.Variable -> ExpInp e -> O (A.Structured A.Process)
+(*!), (*:=) :: (Castable r A.Process, CanBeExpression e) => ExpInp A.Variable -> ExpInp e -> O r
 (*!) bch bsrc = do
   ch <- liftExpInp bch
   src <- liftExpInp bsrc >>= (liftExpInp . expr)
-  return $ A.Only emptyMeta $ A.Output emptyMeta ch [A.OutExpression emptyMeta
-    src]
+  return $ makePlain $ A.Output emptyMeta ch [A.OutExpression emptyMeta src]
 (*:=) bdest bsrc = do
   dest <- liftExpInp bdest
   src <- liftExpInp bsrc >>= (liftExpInp . expr)
-  return $ A.Only emptyMeta $ A.Assign emptyMeta [dest] (A.ExpressionList emptyMeta
-    [src])
+  return $ makePlain $ A.Assign emptyMeta [dest] (A.ExpressionList emptyMeta [src])
 
 infix 8 *:=
 
@@ -307,6 +325,10 @@ instance CanBeExpression A.Expression where
 instance CanBeExpression Int where
   expr = return . A.Literal emptyMeta A.Int . A.IntLiteral emptyMeta . show
 
+instance CanBeExpression Bool where
+  expr True = return $ A.True emptyMeta
+  expr False = return $ A.False emptyMeta
+
 instance CanBeExpression e => CanBeExpression (ExpInp e) where
   expr = join . liftM expr