add test for mergePairs

teavm-classlib/src/test/java/org/teavm/classlib/impl/unicode/UnicodeSupportTest.java

@@ -0,0 +1,20 @@
+package org.teavm.classlib.impl.unicode;
+
+import static org.junit.Assert.assertFalse;
+
+public class UnicodeSupportTest {
+
+    private static boolean pairsEqual(final int[] pairs, final int index1, final int index2) {
+        return pairs[index1] == pairs[index2] && pairs[index1 + 1] == pairs[index2 + 1];
+    }
+
+    @Test
+    public void test_getDigitValues() {
+        final int[] digitValues = UnicodeSupport.getDigitValues();
+        if (digitValues.length >= 4) {
+            // there are no duplicates, so the last two pairs should not be identical
+            assertFalse(pairsEqual(digitValues, digitValues.length - 4, digitValues.length - 2));
+        }
+    }
+
+}