Add test for util.byteToChar() and fix error msg.

testing/resources/javascript/util_bytetochar.in

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@@ skipping 16 matching lines @@
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 % JS program to exexute
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-app.alert('Applying to util itself - should succeed');
+function TestOneInput(x) {
+  try {
+    var s = util.byteToChar(x);
+    if (s.length) {
+      s = s.charCodeAt(0);
+    }
+    app.alert(x + " => " + s);
+  }
+  catch (e) {
+    app.alert(x + ": Caught error: " + e);
+  }
+}
+TestOneInput(0);
+TestOneInput(65);
+TestOneInput(127);
+TestOneInput(128);
+TestOneInput(255);
+TestOneInput(256);
+TestOneInput(40000000);
+TestOneInput(-1);
 try {
-  app.alert(util.byteToChar.apply(util, [65]));
+  util.byteToChar();
 }
 catch (e) {
-  app.alert('Caught: ' + e);
+  app.alert("Caught expected error: " + e);
 }
-
-app.alert('Applying to array - should throw');
 try {
-  app.alert(util.byteToChar.apply([], [65]));
+  util.byteToChar({x:39});
 }
 catch (e) {
-  app.alert('Caught: ' + e);
-}
-
-app.alert('Applying to number - should throw');
-try {
-  app.alert(util.byteToChar.apply(7, [65]));
-}
-catch (e) {
-  app.alert('Caught: ' + e);
-}
-
-app.alert('Applying to wrong native obj - should throw');
-try {
-  app.alert(util.byteToChar.apply(app, [65]));
-}
-catch (e) {
-  app.alert('Caught: ' + e);
+  app.alert("Caught expected error: " + e);
 }
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