Test build: JDK 10 build 41
Test env: Mac 10.13 with ar_SA locale.

Error message:
Expected string:
line \u0660: \u0661
Actual string:
line 0: 1
java.lang.Exception: Incorrect message string
at MessageFormatting.main(MessageFormatting.java:55)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)
at java.base/java.lang.Thread.run(Thread.java:844)

JavaTest Message: Test threw exception: java.lang.Exception: Incorrect message string
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.Exception: Incorrect message string

L65: MessageFormat format = new MessageFormat(str) uses system default locale which is ar_SA to construct a MessageFormat which uses ARABIC-INDIC digits(\u0660~\u0669), not (0~9) to display the numbers.
Suggest to use MessageFormat​(String pattern, Locale locale) and specify en_US locale to construct a MessageFormat.