public void test_negate() { ObjDoublePredicate<String> fn1 = (a, b) -> b > 3; ObjDoublePredicate<String> negate = fn1.negate(); assertEquals(fn1.test("a", 2.3d), false); assertEquals(fn1.test("a", 3.2d), true); assertEquals(negate.test("a", 2.3d), true); assertEquals(negate.test("a", 3.2d), false); }