more tests for digesting queries

haskell-experiments/test/Test/Datalog/DigestedQuerySpec.hs

@@ -17,7 +17,7 @@ import Datalog.DigestedQuery (digestQuery)
 spec :: Spec
 spec = do
   describe "DigestedQuery" $ do
-    it "can digest basic queries" $ do
+    it "can digest a basic query" $ do
       digestQuery "?- parent(alice,X)." `shouldBe` DigestedQuery {
           allBoundVariables = ["X"],
           numSoughtVariables = 1,
@@ -31,3 +31,46 @@ spec = do
             }
           ]
         }
+    it "can digest a query with all variables explicitly sought" $ do
+      digestQuery "?- knows(a,X), friend(X,Y) → X,Y." `shouldBe` DigestedQuery {
+          allBoundVariables = ["X", "Y"],
+          numSoughtVariables = 2,
+          conditions = [
+            DigestedQueryCondition {
+              __relation = "knows",
+              _entries = [
+                DigestedQueryEntryConstant $ Sym "a",
+                DigestedQueryEntryVariable 0
+              ]
+            },
+            DigestedQueryCondition {
+              __relation = "friend",
+              _entries = [
+                DigestedQueryEntryVariable 0,
+                DigestedQueryEntryVariable 1
+              ]
+            }
+          ]
+        }
+    it "can digest a query with unsought variables" $ do
+      digestQuery "?- edge(A,B), edge(B,C) → A,C ." `shouldBe` DigestedQuery {
+          allBoundVariables = ["A", "C", "B"],
+          numSoughtVariables = 2,
+          conditions = [
+            DigestedQueryCondition {
+              __relation = "edge",
+              _entries = [
+                DigestedQueryEntryVariable 0,
+                DigestedQueryEntryVariable 2
+              ]
+            },
+            DigestedQueryCondition {
+              __relation = "edge",
+              _entries = [
+                DigestedQueryEntryVariable 2,
+                DigestedQueryEntryVariable 1
+              ]
+            }
+          ]
+        }
+