fix: expose Kraken errors in KrakenException message

library/src/main/java/dev/andstuff/kraken/api/endpoint/KrakenException.java

@@ -15,11 +15,12 @@ public class KrakenException extends RuntimeException {
     private final List<String> errors;
 
     /**
-     * Creates an exception holding the errors returned by Kraken.
+     * Creates an exception holding the errors returned by Kraken, whose message lists them separated by commas.
      *
      * @param errors the errors, as returned by Kraken
      */
     public KrakenException(List<String> errors) {
+        super(errors == null ? null : String.join(", ", errors));
         this.errors = errors;
     }
 }

library/src/test/java/dev/andstuff/kraken/api/endpoint/KrakenExceptionTest.java

@@ -0,0 +1,36 @@
+package dev.andstuff.kraken.api.endpoint;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class KrakenExceptionTest {
+
+    @Test
+    void should_use_error_as_message_when_kraken_returns_one_error() {
+        KrakenException unit = new KrakenException(List.of("EAPI:Invalid key"));
+
+        assertThat(unit).hasMessage("EAPI:Invalid key");
+        assertThat(unit.getErrors()).containsExactly("EAPI:Invalid key");
+    }
+
+    @Test
+    void should_join_errors_in_message_when_kraken_returns_several_errors() {
+        KrakenException unit = new KrakenException(List.of("EGeneral:Invalid arguments", "EGeneral:Permission denied"));
+
+        assertThat(unit).hasMessage("EGeneral:Invalid arguments, EGeneral:Permission denied");
+    }
+
+    @Test
+    void should_have_no_message_when_kraken_returns_no_error_field() {
+        KrakenException unit = new KrakenException(null);
+
+        assertThat(unit.getMessage()).isNull();
+        assertThat(unit.getErrors()).isNull();
+    }
+}