void () { Map<Object, Object> map = factory.create(); String key = "key"; Assume.assumeTrue("Does not support null values", isSupported(() -> map.put(key, null))); Assert.assertEquals(1, map.size()); Assert.assertTrue("Null val not found", map.containsValue(null)); Assert.assertTrue("Null val not found by key", map.containsKey(key)); Assert.assertEquals(1, map.size()); Assert.assertNull("Val differs", map.get(key)); Assert.assertEquals(1, map.size()); Assert.assertNull("Removed val differs", map.remove(key)); Assert.assertEquals(0, map.size()); map.put(key, null); Assert.assertTrue("Removed val differs", map.remove(key, null)); Assert.assertEquals(0, map.size()); }