add a round-trip test for players

elm.json

@@ -27,7 +27,9 @@
         }
     },
     "test-dependencies": {
-        "direct": {},
+        "direct": {
+            "elm-explorations/test": "1.2.2"
+        },
         "indirect": {}
     }
 }

tests/PlayerTest.elm

@@ -0,0 +1,24 @@
+module PlayerTest exposing (..)
+
+import Expect
+import Fuzz exposing (Fuzzer)
+import Json.Decode as Decode
+import Player exposing (Player)
+import Test exposing (..)
+
+
+roundTripDecoderTest : Test
+roundTripDecoderTest =
+    fuzz playerFuzzer "encode and decode are symmetrical" <|
+        \player ->
+            Player.encode player
+                |> Decode.decodeValue Player.decoder
+                |> Expect.equal (Ok player)
+
+
+playerFuzzer : Fuzzer Player
+playerFuzzer =
+    Fuzz.map3 Player
+        Fuzz.string
+        (Fuzz.intRange 1000 3000)
+        (Fuzz.intRange 0 50)