From b2d7fce66be7904246dc2870a7575340acf3d110 Mon Sep 17 00:00:00 2001
From: Tom Anderson <twic@urchin.earth.li>
Date: Mon, 16 May 2016 00:06:52 +0100
Subject: [PATCH] Produce a more legible failure message when multidimensional
 arrays are of different lengths

Closes #1300
---
 .../junit/internal/ComparisonCriteria.java    | 40 ++++++++++++++-----
 .../junit/tests/assertion/AssertionTest.java  | 36 +++++++++++++----
 2 files changed, 60 insertions(+), 16 deletions(-)

diff --git a/src/main/java/org/junit/internal/ComparisonCriteria.java b/src/main/java/org/junit/internal/ComparisonCriteria.java
index fa7840cf9b7b..ed1c674907cb 100644
--- a/src/main/java/org/junit/internal/ComparisonCriteria.java
+++ b/src/main/java/org/junit/internal/ComparisonCriteria.java
@@ -81,8 +81,8 @@ private void arrayEquals(String message, Object expecteds, Object actuals, boole
         }
 
         if (actualsLength != expectedsLength) {
-            Object expected = getArrayElementOrSentinel(expecteds, expectedsLength, prefixLength);
-            Object actual = getArrayElementOrSentinel(actuals, actualsLength, prefixLength);
+            Object expected = getToStringableArrayElement(expecteds, expectedsLength, prefixLength);
+            Object actual = getToStringableArrayElement(actuals, actualsLength, prefixLength);
             try {
                 Assert.assertEquals(expected, actual);
             } catch (AssertionError e) {
@@ -91,15 +91,37 @@ private void arrayEquals(String message, Object expecteds, Object actuals, boole
         }
     }
 
-    private static final Object END_OF_ARRAY_SENTINEL = new Object() {
-        @Override
-        public String toString() {
-            return "end of array";
+    private static final Object END_OF_ARRAY_SENTINEL = objectWithToString("end of array");
+
+    private Object getToStringableArrayElement(Object array, int length, int index) {
+        if (index < length) {
+            Object element = Array.get(array, index);
+            if (isArray(element)) {
+                return objectWithToString(componentTypeName(element.getClass()) + "[" + Array.getLength(element) + "]");
+            } else {
+                return element;
+            }
+        } else {
+            return END_OF_ARRAY_SENTINEL;
         }
-    };
+    }
 
-    private Object getArrayElementOrSentinel(Object array, int length, int index) {
-        return index < length ? Array.get(array, index) : END_OF_ARRAY_SENTINEL;
+    private static Object objectWithToString(final String string) {
+        return new Object() {
+            @Override
+            public String toString() {
+                return string;
+            }
+        };
+    }
+
+    private String componentTypeName(Class<?> arrayClass) {
+        Class<?> componentType = arrayClass.getComponentType();
+        if (componentType.isArray()) {
+            return componentTypeName(componentType) + "[]";
+        } else {
+            return componentType.getName();
+        }
     }
 
     private boolean isArray(Object expected) {
diff --git a/src/test/java/org/junit/tests/assertion/AssertionTest.java b/src/test/java/org/junit/tests/assertion/AssertionTest.java
index b13f79eac349..fabda1336761 100755
--- a/src/test/java/org/junit/tests/assertion/AssertionTest.java
+++ b/src/test/java/org/junit/tests/assertion/AssertionTest.java
@@ -243,27 +243,49 @@ public void multiDimensionalArraysAreNotEqualNoMessage() {
 
     @Test
     public void twoDimensionalArraysDifferentOuterLengthNotEqual() {
-        Object[] extraArray = {true};
         assertArrayEqualsFailure(
                 "not equal",
-                new Object[][]{extraArray, {}},
+                new Object[][]{{true}, {}},
                 new Object[][]{{}},
                 "not equal: array lengths differed, expected.length=1 actual.length=0; arrays first differed at element [0][0]; expected:<true> but was:<end of array>");
         assertArrayEqualsFailure(
                 "not equal",
-                new Object[][]{{}, extraArray},
+                new Object[][]{{}, {true}},
                 new Object[][]{{}},
-                "not equal: array lengths differed, expected.length=2 actual.length=1; arrays first differed at element [1]; expected:<" + extraArray.toString() + "> but was:<end of array>");
+                "not equal: array lengths differed, expected.length=2 actual.length=1; arrays first differed at element [1]; expected:<java.lang.Object[1]> but was:<end of array>");
         assertArrayEqualsFailure(
                 "not equal",
                 new Object[][]{{}},
-                new Object[][]{extraArray, {}},
+                new Object[][]{{true}, {}},
                 "not equal: array lengths differed, expected.length=0 actual.length=1; arrays first differed at element [0][0]; expected:<end of array> but was:<true>");
         assertArrayEqualsFailure(
                 "not equal",
                 new Object[][]{{}},
-                new Object[][]{{}, extraArray},
-                "not equal: array lengths differed, expected.length=1 actual.length=2; arrays first differed at element [1]; expected:<end of array> but was:<" + extraArray.toString() + ">");
+                new Object[][]{{}, {true}},
+                "not equal: array lengths differed, expected.length=1 actual.length=2; arrays first differed at element [1]; expected:<end of array> but was:<java.lang.Object[1]>");
+    }
+
+    @Test
+    public void primitiveArraysConvertedToStringCorrectly() {
+        assertArrayEqualsFailure(
+                "not equal",
+                new boolean[][]{{}, {true}},
+                new boolean[][]{{}},
+                "not equal: array lengths differed, expected.length=2 actual.length=1; arrays first differed at element [1]; expected:<boolean[1]> but was:<end of array>");
+        assertArrayEqualsFailure(
+                "not equal",
+                new int[][]{{}, {23}},
+                new int[][]{{}},
+                "not equal: array lengths differed, expected.length=2 actual.length=1; arrays first differed at element [1]; expected:<int[1]> but was:<end of array>");
+    }
+
+    @Test
+    public void twoDimensionalArraysConvertedToStringCorrectly() {
+        assertArrayEqualsFailure(
+                "not equal",
+                new Object[][][]{{}, {{true}}},
+                new Object[][][]{{}},
+                "not equal: array lengths differed, expected.length=2 actual.length=1; arrays first differed at element [1]; expected:<java.lang.Object[][1]> but was:<end of array>");
     }
 
     @Test