Refactor custom currency tests

Author: kipcole9

test/custom_currency_test.exs

@@ -1,12 +1,6 @@
 defmodule Money.CustomCurrencyTest do
   use ExUnit.Case
 
-  setup do
-    Cldr.Currency.start_link()
-    {:ok, _currency} = Cldr.Currency.new(:ABCD, name: "ABCD", digits: 0)
-    :ok
-  end
-
   test "Exchange rate conversion for a custom currency fails" do
     m1 = Money.new(:ABCD, 10)
 

test/money_test.exs

@@ -191,8 +191,8 @@ defmodule MoneyTest do
   end
 
   test "creating a money struct with an invalid binary currency code returns error tuple" do
-    assert Money.new("ABCD", 100) ==
-             {:error, {Money.UnknownCurrencyError, "The currency \"ABCD\" is invalid"}}
+    assert Money.new("XYZABC", 100) ==
+             {:error, {Money.UnknownCurrencyError, "The currency \"XYZABC\" is invalid"}}
   end
 
   test "string output of money is correctly formatted" do

test/test_helper.exs

@@ -1 +1,3 @@
 ExUnit.start()
+{:ok, _pid} = Cldr.Currency.start_link()
+{:ok, _currency} = Cldr.Currency.new(:ABCD, name: "ABCD", digits: 0)