Add a few test cases

test/known_problems/should_pass/elixir_list_first.erl

@@ -0,0 +1,17 @@
+-module(elixir_list_first).
+
+-export([f/0]).
+
+% This is how List.first/1 is defined in Elixir
+-spec first([]) -> nil;
+           ([Elem, ...]) -> Elem.
+first([]) -> nil;
+first([Element | _]) -> Element.
+
+-spec f() -> ok.
+f() ->
+    first(some_list()),
+    ok.
+
+-spec some_list() -> list().
+some_list() -> [anything].

test/known_problems/should_pass/refine_comparison_should_pass.erl

@@ -0,0 +1,13 @@
+-module(refine_comparison_should_pass).
+
+-export([comp_map_value3/1]).
+
+-type my_map() :: #{value := integer() | nil}.
+
+-spec comp_map_value3(my_map()) -> integer().
+comp_map_value3(State) when map_get(value, State) /= nil ->
+    case State of
+        #{value := Val} ->
+            Val + 1
+    end;
+comp_map_value3(#{value := nil}) -> 0.

test/should_pass/refine_comparison.erl

@@ -28,3 +28,20 @@ compatom1(_) -> ok.
 -spec compatom2(a | b | c | pid()) -> a | c | pid().
 compatom2(X) when X =/= b -> X;
 compatom2(_) -> a.
+
+-spec compatom3(a | b | c | pid()) -> a | c | pid().
+compatom3(X) when X /= b -> X;
+compatom3(_) -> a.
+
+-type my_map() :: #{value := integer() | nil}.
+
+-spec comp_map_value1(my_map()) -> integer().
+comp_map_value1(State) when map_get(value, State) /= nil ->
+    Val = map_get(value, State),
+    Val + 1;
+comp_map_value1(#{value := nil}) -> 0.
+
+-spec comp_map_value2(my_map()) -> integer().
+comp_map_value2(#{value := Val}) when Val /= nil ->
+    Val + 1;
+comp_map_value2(#{value := nil}) -> 0.