Rework test fixtures

Next, grow the amount of data tested to find bugs in the tests with
non-repeatable map ordering

src/test/java/org/apache/commons/collections4/multimap/AbstractMultiValuedMapTest.java

@@ -520,7 +520,7 @@ public MultiValuedMap<K, V> getMap() {
      */
     @SuppressWarnings("unchecked")
     public K[] getSampleKeys() {
-        final Object[] result = { "k0", "k0", "k1", "k1", "k2", "k2" };
+        final Object[] result = new Object[getSampleSize()];
         int k = 0;
         for (int i = 0; i < result.length; i += 2, k++) {
             final String key = "k" + Integer.valueOf(k);
@@ -530,6 +530,10 @@ public K[] getSampleKeys() {
         return (K[]) result;
     }
 
+    public int getSampleSize() {
+        return 6;
+    }
+
     /**
      * Returns the set of values in the mappings used to test the map. This
      * method must return an array with the same length as
@@ -538,10 +542,7 @@ public K[] getSampleKeys() {
      */
     @SuppressWarnings("unchecked")
     public V[] getSampleValues() {
-        final Object[] result = {
-            "v1_b", "v0_b", "v1_a", "v1_b",
-            "v2_a", "v2_b"
-        };
+        final Object[] result = new Object[getSampleSize()];
         int k = 0;
         for (int i = 0; i < result.length; i += 2, k++) {
             final String key = "v" + Integer.valueOf(k);