Investigate the stability of build

[tngan]

It sometimes doesn't pass through the build because of the failure in schema validation.

[tngan]

Error: A JNI error has occurred, please check your installation and try again
Exception 
in thread "main" 
Error: A JNI error has occurred, please check your installation and try again
Exception 
in thread "main" 
java.lang.ClassFormatError: Truncated class file
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
java.lang.ClassFormatError: Truncated class file
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:495)

[tngan]

I have figured out why it happens. The validator library is not shipped with compiled class file, and the tests are running concurrently with ava. When yarn test is running, there is no compiled class file initially, therefore, for each test, it will spawn a javac support/XMLValidator.java command inside that library, so that the validator won't work at all.