Fix fetching message from caused throwable

src/main/java/pl/wavesoftware/eid/exceptions/EidRuntimeException.java

@@ -15,6 +15,8 @@
  */
 package pl.wavesoftware.eid.exceptions;
 
+import javax.annotation.Nullable;
+
 /**
  * <strong>This class shouldn't be used in any public API or library.</strong> It is designed to be used for in-house development
  * of end user applications which will report Bugs in standardized error pages or post them to issue tracker.
@@ -118,7 +120,17 @@ public Class<? extends RuntimeException> getStandardJdkClass() {
     }
 
     private static String message(Throwable cause) {
-        return cause.getLocalizedMessage();
+        String msg = coalesce(cause.getLocalizedMessage(), cause.getMessage());
+        return coalesce(msg, cause.toString());
+    }
+
+    @Nullable
+    private static <T> T coalesce(@Nullable T first, @Nullable T second) {
+        if (first == null) {
+            return second;
+        } else {
+            return first;
+        }
     }
 
 }

src/test/java/pl/wavesoftware/eid/exceptions/ExceptionsTest.java

@@ -15,18 +15,20 @@
  */
 package pl.wavesoftware.eid.exceptions;
 
-import java.lang.reflect.Constructor;
-import java.lang.reflect.InvocationTargetException;
-import java.util.List;
-import java.util.Map;
-import static org.assertj.core.api.Assertions.assertThat;
 import org.assertj.core.util.Lists;
 import org.assertj.core.util.Maps;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 import org.junit.runners.Parameterized.Parameters;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  *
  * @author Krzysztof Suszyński <krzysztof.suszynski@wavesoftware.pl>
@@ -47,7 +49,7 @@ private static Map<Class<? extends EidRuntimeException>, Class<? extends Runtime
     }
 
     private static List<Object[]> getArguments() {
-        Throwable cause = new InterruptedException();
+        Throwable cause = new InterruptedException("A testing message");
         String eid = "20150718:112954";
         String ref = "PL-981";
         Eid id = new Eid(eid);
@@ -148,10 +150,24 @@ public void testGetStandardJdkClass() {
         assertThat(jdkCls).isEqualTo(jdkClass);
     }
 
+    @Test
+    public void testMessage() {
+        // given
+        EidRuntimeException exception = construct();
+        boolean hasCause = exception.getCause() != null;
+
+        // then
+        assertThat(exception).hasMessageContaining("20150718:112954");
+        if (hasCause) {
+            assertThat(exception).hasMessageContaining("A testing message");
+        }
+    }
+
     @Test
     public void testConstruction() {
         // given
         EidRuntimeException exception = construct();
+
         // then
         assertThat(exception).isNotNull();
         assertThat(exception).isExactlyInstanceOf(eidClass);