improve error msg

Author: dcapwell

accord-core/src/test/java/accord/utils/Property.java

@@ -183,7 +183,7 @@ private static Object normalizeValue(Object value)
         }
     }
 
-    private static String propertyError(Common<?> input, Throwable cause, Object... values)
+    private static StringBuilder propertyErrorCommon(Common<?> input, Throwable cause)
     {
         StringBuilder sb = new StringBuilder();
         // return "Seed=" + seed + "\nExamples=" + examples;
@@ -201,6 +201,12 @@ private static String propertyError(Common<?> input, Throwable cause, Object...
                 msg = cause.getClass().getCanonicalName();
             sb.append(msg).append('\n');
         }
+        return sb;
+    }
+
+    private static String propertyError(Common<?> input, Throwable cause, Object... values)
+    {
+        StringBuilder sb = propertyErrorCommon(input, cause);
         if (values != null)
         {
             sb.append("Values:\n");
@@ -210,6 +216,18 @@ private static String propertyError(Common<?> input, Throwable cause, Object...
         return sb.toString();
     }
 
+    private static String statefulPropertyError(StatefulBuilder input, Throwable cause, Object state, List<String> history)
+    {
+        StringBuilder sb = propertyErrorCommon(input, cause);
+        sb.append("Steps: ").append(input.steps).append('\n');
+        sb.append("Values:\n");
+        sb.append("\tState: ").append(state).append(": ").append(state == null ? "unknown type" : state.getClass().getCanonicalName()).append('\n');
+        sb.append("\tHistory:").append('\n');
+        for (var event : history)
+            sb.append("\t\t").append(event).append('\n');
+        return sb.toString();
+    }
+
     public interface FailingConsumer<A>
     {
         void accept(A value) throws Exception;
@@ -449,7 +467,7 @@ public <State, SystemUnderTest> void check(Commands<State, SystemUnderTest> comm
                 }
                 catch (Throwable t)
                 {
-                    throw new PropertyError(propertyError(this, t, state, history), t);
+                    throw new PropertyError(statefulPropertyError(this, t, state, history), t);
                 }
                 if (pure)
                 {