### Question:
AsciiStringListUtil { @Nullable public static String iterableToString(@Nullable Iterable<String> strings) { if (strings == null) { return null; } Set<String> stringSet = new LinkedHashSet<>(); for (String str : strings) { checkArgument(!TextUtils.isEmpty(str), "individual scopes cannot be null or empty"); stringSet.add(str); } if (stringSet.isEmpty()) { return null; } return TextUtils.join(" ", stringSet); } private  AsciiStringListUtil(); @Nullable static String iterableToString(@Nullable Iterable<String> strings); @Nullable static Set<String> stringToSet(@Nullable String spaceDelimitedStr);  }### Answer:
@Test public void testScopeIterableToString() throws Exception { assertEquals(SCOPE_STRING, AsciiStringListUtil.iterableToString(SCOPES)); }
@Test public void testScopeIterableToString_nullIterable() throws Exception { assertNull(AsciiStringListUtil.iterableToString(null)); }