Sync flatten-array exercise

exercises/practice/flatten-array/.meta/tests.toml

@@ -9,9 +9,15 @@
 # As user-added comments (using the # character) will be removed when this file
 # is regenerated, comments can be added via a `comment` key.
 
+[8c71dabd-da60-422d-a290-4a571471fb14]
+description = "empty"
+
 [d268b919-963c-442d-9f07-82b93f1b518c]
 description = "no nesting"
 
+[3f15bede-c856-479e-bb71-1684b20c6a30]
+description = "flattens a nested array"
+
 [c84440cc-bb3a-48a6-862c-94cf23f2815d]
 description = "flattens array with just integers present"
 
@@ -21,6 +27,15 @@ description = "5 level nesting"
 [d572bdba-c127-43ed-bdcd-6222ac83d9f7]
 description = "6 level nesting"
 
+[0705a8e5-dc86-4cec-8909-150c5e54fa9c]
+description = "null values are omitted from the final result"
+
+[c6cf26de-8ccd-4410-84bd-b9efd88fd2bc]
+description = "consecutive null values at the front of the list are omitted from the final result"
+
+[382c5242-587e-4577-b8ce-a5fb51e385a1]
+description = "consecutive null values in the middle of the list are omitted from the final result"
+
 [ef1d4790-1b1e-4939-a179-51ace0829dbd]
 description = "6 level nest list with null values"
 

exercises/practice/flatten-array/test.sml

@@ -1,4 +1,4 @@
-(* version 1.1.0 *)
+(* version 1.2.0 *)
 
 use "testlib.sml";
 use "flatten-array.sml";
@@ -8,13 +8,27 @@ fun x |> f = f x
 
 val testsuite =
   describe "flatten-array" [
+    test "empty"
+      (fn _ => let
+        val nested = List []
+      in
+        flatten nested |> Expect.equalTo []
+      end),
+
     test "no nesting"
       (fn _ => let
         val nested = List [Elem 0, Elem 1, Elem 2]
       in
         flatten nested |> Expect.equalTo [0, 1, 2]
       end),
 
+    test "flattens a nested array"
+      (fn _ => let
+        val nested = List [List [List []]]
+      in
+        flatten nested |> Expect.equalTo []
+      end),
+
     test "flattens array with just integers present"
       (fn _ => let
         val nested = List [Elem 1,
@@ -51,6 +65,27 @@ val testsuite =
         flatten nested |> Expect.equalTo [1, 2, 3, 4, 5, 6, 7, 8]
       end),
 
+    test "Empty values are omitted from the final result"
+      (fn _ => let
+        val nested = List [Elem 1, Elem 2, Empty]
+      in
+        flatten nested |> Expect.equalTo [1, 2]
+      end),
+
+    test "consecutive Empty values at the front of the list are omitted from the final result"
+      (fn _ => let
+        val nested = List [Empty, Empty, Elem 3]
+      in
+        flatten nested |> Expect.equalTo [3]
+      end),
+
+    test "consecutive Empty values in the middle of the list are omitted from the final result"
+      (fn _ => let
+        val nested = List [Elem 1, Empty, Empty, Elem 4]
+      in
+        flatten nested |> Expect.equalTo [1, 4]
+      end),
+
     test "6 level nest list with Empty values"
       (fn _ => let
         val nested = List [Elem 0,