DummyUnionType example

                new DateTimeNormalizer(),
                new ObjectNormalizer($classMetadataFactory, null, null, $extractor, new ClassDiscriminatorFromClassMetadata($classMetadataFactory)),
            ],
            ['json' => new JsonEncoder()]
        );

        $actual = $serializer->deserialize('{ "changed": null }', DummyUnionType::class, 'json', [
            DateTimeNormalizer::FORMAT_KEY => \DateTimeinterface::ATOM,
        ]);

        $this->assertEquals((new DummyUnionType())->setChanged(null), $actual, 'Union type denormalization first case failed.');

        $actual = $serializer->deserialize('{ "changed": "2022-03-22T16:15:05+0000" }', DummyUnionType::class, 'json', [
            DateTimeNormalizer::FORMAT_KEY => \DateTimeinterface::ATOM,
        ]);

        $expectedDateTime = \DateTimeImmutable::createFromFormat(\DateTimeinterface::ATOM, '2022-03-22T16:15:05+0000');
        $this->assertEquals((new DummyUnionType())->setChanged($expectedDateTime), $actual, 'Union type denormalization second case failed.');

        $actual = $serializer->deserialize('{ "changed": false }', DummyUnionType::class, 'json', [
            DateTimeNormalizer::FORMAT_KEY => \DateTimeinterface::ATOM,
        ]);