Copy in old highligthable spec from the monolith

tests/Spec/Nri/Ui/Highlightable.elm

@@ -0,0 +1,52 @@
+module Spec.Nri.Ui.Highlightable exposing (spec)
+
+import Expect
+import Fuzz exposing (..)
+import Nri.Ui.Highlightable.V1 as Highlightable
+import Nri.Ui.Highlighter.V2 as Highlighter
+import String.Extra
+import Test exposing (..)
+
+
+spec : Test
+spec =
+    describe "Highlightable"
+        [ describe "roundtrip from initFragment via toTuplesByFragment"
+            [ fuzz (list string) "toTuplesByFragment (initFragment [str]) ... == [str]" <|
+                \strings ->
+                    let
+                        fragment =
+                            strings
+                                |> List.map (Tuple.pair [])
+                                |> Highlightable.initFragment Nothing 0
+
+                        roundtripText =
+                            Highlighter.asFragmentTuples fragment
+                                |> List.head
+                                |> Maybe.map Tuple.second
+
+                        expected =
+                            String.Extra.nonEmpty (String.join "" strings)
+                    in
+                    Expect.equal roundtripText expected
+            ]
+        , fuzz Fuzz.string "splitWords" <|
+            \a ->
+                let
+                    expected =
+                        String.split " " a
+                            |> List.length
+                            |> (*) 2
+                            |> (\x ->
+                                    if x > 1 then
+                                        x - 1
+
+                                    else
+                                        x
+                               )
+                            |> max 0
+                in
+                Highlightable.splitWords a
+                    |> List.length
+                    |> Expect.equal expected
+        ]