### Question:
LinkageProblem { public String formatSymbolProblem() { String result = symbol + " " + symbolProblemMessage; if (targetClass != null) { String jarInfo = "(" + getTargetClass().getClassPathEntry() + ") "; result = jarInfo + result; } return result; } LinkageProblem(
      String symbolProblemMessage, ClassFile sourceClass, Symbol symbol, ClassFile targetClass); Symbol getSymbol(); ClassFile getSourceClass(); @Nullable ClassFile getTargetClass(); @Override boolean equals(Object other); @Override int hashCode(); @Override String toString(); String formatSymbolProblem(); static ImmutableMap<String, ImmutableSet<String>> groupBySymbolProblem(
      Iterable<LinkageProblem> linkageProblems); static String formatLinkageProblems(
      Set<LinkageProblem> linkageProblems, @Nullable ClassPathResult classPathResult);  }### Answer:
@Test public void testFormatSymbolProblem() { assertEquals( "Class java.lang.Integer is not found", classLinkageProblem1.formatSymbolProblem()); assertEquals( classLinkageProblem1.formatSymbolProblem(), classLinkageProblem2.formatSymbolProblem()); }