Translate Engine utilities tests.

pkg/analyzer/lib/src/generated/java_engine.dart

 library java.engine;
 
 import 'interner.dart';
 import 'java_core.dart';
 
 /**
  * A predicate is a one-argument function that returns a boolean value.
  */
 typedef bool Predicate<E>(E argument);
 
@@ skipping 22 matching lines @@
     }
     return true;
   }
   static bool isEmpty(String s) {
     return s == null || s.isEmpty;
   }
   static String substringBefore(String str, String separator) {
     if (str == null || str.isEmpty) {
       return str;
     }
+    if (separator == null) {
+      return str;
+    }
     int pos = str.indexOf(separator);
     if (pos < 0) {
       return str;
     }
     return str.substring(0, pos);
   }
   static endsWithChar(String str, int c) {
     int length = str.length;
     return length > 0 && str.codeUnitAt(length - 1) == c;
   }
@@ skipping 272 matching lines @@
       if (cause != null) {
         buffer.write('Caused by ');
         cause._writeOn(buffer);
       }
     } else {
       buffer.writeln(exception.toString());
       buffer.writeln(stackTrace.toString());
     }
   }
 }