@Test
public void testOneUnwrapDisablesAnother() throws Exception {

  final String program = "void main() { { int x; } { float x; } }";
  final TranslationUnit tu = ParseHelper.parse(program);
  List<UnwrapReductionOpportunity> ops = UnwrapReductionOpportunities
      .findOpportunities(MakeShaderJobFromFragmentShader.make(tu),
      new ReducerContext(false,
          ShadingLanguageVersion.GLSL_440, new SameValueRandom(false, 0),
          new IdGenerator()));
  assertEquals(2, ops.size());
  assertTrue(ops.get(0).preconditionHolds());
  assertTrue(ops.get(1).preconditionHolds());
  ops.get(0).applyReduction();
  assertFalse(ops.get(1).preconditionHolds());
}