Add an empty dummy exchange rate to prevent warning logs

pricenode/src/main/java/bisq/price/spot/providers/CoinMarketCap.java

@@ -25,7 +25,7 @@
 
 import java.time.Duration;
 
-import java.util.Collections;
+import java.util.HashSet;
 import java.util.Set;
 
 /**
@@ -40,14 +40,16 @@ public CoinMarketCap() {
     }
 
     /**
-     * Returns an empty Set for the CoinMarketCap price provider.
+     * Returns a Set with a non existing symbol for the CoinMarketCap price provider.
      * Price data of CMC provider is not used in the client anymore, except for the last update timestamp.
+     * To prevent a unnecessary warning log in that case we have to pass at least one element.
      *
      * @return Empty Set
      */
     @Override
     public Set<ExchangeRate> doGet() {
-
-        return Collections.emptySet();
+        HashSet<ExchangeRate> exchangeRates = new HashSet<>();
+        exchangeRates.add(new ExchangeRate("NON_EXISTING_SYMBOL", 0, 0L, "CMC"));
+        return exchangeRates;
     }
 }

pricenode/src/test/java/bisq/price/spot/ExchangeRateServiceTest.java

@@ -0,0 +1,83 @@
+/*
+ * This file is part of Bisq.
+ *
+ * Bisq is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * Bisq is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Bisq. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package bisq.price.spot;
+
+import java.time.Duration;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.junit.Test;
+
+public class ExchangeRateServiceTest {
+
+    @Test
+    public void getAllMarketPrices_withNoExchangeRates_logs_Exception() {
+        ExchangeRateProvider dummyProvider = new ExchangeRateProvider("Dummy", "YUM", Duration.ofDays(1)) {
+
+            @Override
+            public boolean isRunning() {
+                return true;
+            }
+
+            @Override
+            protected Set<ExchangeRate> doGet() {
+                return Collections.emptySet();
+            }
+        };
+
+        dummyProvider.start();
+        dummyProvider.stop();
+
+        List<ExchangeRateProvider> providerList = new ArrayList<>(Collections.singleton(dummyProvider));
+
+        ExchangeRateService service = new ExchangeRateService(providerList);
+
+        service.getAllMarketPrices();
+    }
+
+    @Test
+    public void getAllMarketPrices_withSingleExchangeRate() {
+        ExchangeRateProvider dummyProvider = new ExchangeRateProvider("Dummy", "YUM", Duration.ofDays(1)) {
+
+            @Override
+            public boolean isRunning() {
+                return true;
+            }
+
+            @Override
+            protected Set<ExchangeRate> doGet() {
+                HashSet<ExchangeRate> exchangeRates = new HashSet<>();
+                exchangeRates.add(new ExchangeRate("DUM", 0, 0L, "Dummy"));
+                return exchangeRates;
+            }
+        };
+
+        dummyProvider.start();
+        dummyProvider.stop();
+
+        List<ExchangeRateProvider> providerList = new ArrayList<>(Collections.singleton(dummyProvider));
+
+        ExchangeRateService service = new ExchangeRateService(providerList);
+
+        service.getAllMarketPrices();
+    }
+}