Add currency tests.

app/Repositories/Currency/CurrencyRepositoryInterface.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace FireflyIII\Repositories\Currency;
+
+
+use FireflyIII\Models\Preference;
+use FireflyIII\Models\TransactionCurrency;
+use Illuminate\Support\Collection;
+
+/**
+ * Interface CurrencyRepositoryInterface
+ *
+ * @package FireflyIII\Repositories\Currency
+ */
+interface CurrencyRepositoryInterface
+{
+
+    /**
+     * @param TransactionCurrency $currency
+     *
+     * @return int
+     */
+    public function countJournals(TransactionCurrency $currency);
+
+    /**
+     * @return Collection
+     */
+    public function get();
+
+    /**
+     * @param Preference $preference
+     *
+     * @return TransactionCurrency
+     */
+    public function getCurrencyByPreference(Preference $preference);
+
+    /**
+     * @param array $data
+     *
+     * @return TransactionCurrency
+     */
+    public function store(array $data);
+
+    /**
+     * @param TransactionCurrency $currency
+     * @param array               $data
+     *
+     * @return TransactionCurrency
+     */
+    public function update(TransactionCurrency $currency, array $data);
+
+}