Make shrinking print where it's up to when signal (ie. ctrl+c) before exiting

1 files changed, 21 insertions, 4 deletions

diff --git a/src/main/java/au/id/zancanaro/javacheck/junit/Properties.java b/src/main/java/au/id/zancanaro/javacheck/junit/Properties.java
index 64bd9ab..6ff0538 100644
--- a/src/main/java/au/id/zancanaro/javacheck/junit/Properties.java
+++ b/src/main/java/au/id/zancanaro/javacheck/junit/Properties.java
@@ -221,7 +221,13 @@ public class Properties extends BlockJUnit4ClassRunner {
         }
 
         private ShrinkResult shrink(RoseTree<Object[]> failed, Throwable originalEx) {
-            ShrinkResult smallest = new ShrinkResult(failed.getValue(), originalEx);
+            // this array is a mutable container so the shutdown handler can see the new version
+            ShrinkResult[] smallest = new ShrinkResult[]{
+                    new ShrinkResult(failed.getValue(), originalEx)};
+
+            Thread shutdownHandler = makeShutdownHandler(smallest, originalEx);
+            Runtime.getRuntime().addShutdownHook(shutdownHandler);
+
             Iterator<RoseTree<Object[]>> trees = failed.getChildren();
             Set<List<Object>> seenArgs = new HashSet<>();
             while (trees.hasNext()) {
@@ -232,7 +238,7 @@ public class Properties extends BlockJUnit4ClassRunner {
                     } catch (AssumptionViolatedException ex) {
                         // ignore, because it's not useful
                     } catch (Throwable ex) {
-                        smallest = new ShrinkResult(tree.getValue(), ex);
+                        smallest[0] = new ShrinkResult(tree.getValue(), ex);
                         Iterator<RoseTree<Object[]>> children = tree.getChildren();
                         if (children.hasNext()) {
                             trees = children;
@@ -242,7 +248,18 @@ public class Properties extends BlockJUnit4ClassRunner {
                     }
                 }
             }
-            return smallest;
+
+            Runtime.getRuntime().removeShutdownHook(shutdownHandler);
+            return smallest[0];
+        }
+
+        private Thread makeShutdownHandler(ShrinkResult[] smallest, Throwable originalException) {
+            return new Thread(() -> {
+                System.err.println("Signal received while shrinking.\n" +
+                        "Current best shrink is: " + Arrays.toString(smallest[0].args) + "\n" +
+                        "Shrinking exception: " + smallest[0].thrown + "\n" +
+                        "Originally was: " + originalException);
+            });
         }
 
         public void runTest(final Object[] args) throws Throwable {
@@ -276,4 +293,4 @@ public class Properties extends BlockJUnit4ClassRunner {
         }
     }
 
-}
\ No newline at end of file
+}