diff --git a/tests/List/ExtraTests.elm b/tests/List/ExtraTests.elm
new file mode 100644
index 0000000..ba88a77
--- /dev/null
+++ b/tests/List/ExtraTests.elm
@@ -0,0 +1,26 @@
+module List.ExtraTests exposing (..)
+
+import Expect
+import List.Extra exposing (..)
+import Test exposing (..)
+
+
+indexOfTests : Test
+indexOfTests =
+    describe "indexOf"
+        [ test "gives the index when an item is in the list" <|
+            \_ ->
+                [ 1 ]
+                    |> indexOf 1
+                    |> Expect.equal (Just 0)
+        , test "gives the first index when the item is present multiple times" <|
+            \_ ->
+                [ 1, 1 ]
+                    |> indexOf 1
+                    |> Expect.equal (Just 0)
+        , test "does not give an index if the item isn't in the list" <|
+            \_ ->
+                [ 1 ]
+                    |> indexOf 2
+                    |> Expect.equal Nothing
+        ]