[Question] Why is the HalRepresentationModel private and/or how can i work around that?

[thiotes]

I have a service that uses the new HalModelBuilder to enrich an existing RepresentationModel with an additional embedded object. However i can find no way to unit test that service, since the only thing i can return with it is an EntityModel.

I can maybe write an integrationtest by looking at the actual JSON produced by the controller, but i find this somewhat unsatisfactory.

What is the way to go in this situation?

[odrotbohm]

If you're trying to test it on the HalRepresentationModel, aren't you somehow rather testing the builder or the model instance? What's wrong with verifying the output?

[gregturn]

You can register HAL with an ObjectMapper, and serialize it right there. That lets you skip the Spring MVC machinery.

[thiotes]

I am trying to unittest that my service adds the additional embedded object (not that it is added somewhere in the chain). Using the final output means i am not doing a unit test.

Serializing manually in the test is an option i suppose.

Still.. what is the reasoning to make it private? It is weird to me to create a builder and then have it build an Object which does not reflect what i have actually done using the builder.

Its like having a StringBuilder with the toString method returning an Object, and to get your actual String object you need to use a StringBuilderMapper. Why?

[gregturn]

The reasoning is that this project has four public model types: RepresentationModel, EntityModel, CollectionModel, and PagedModel.

Exposing more public facing types introduces additional maintenance. Given that the HalModelBuilder is a relatively new feature, best to get feedback on it's APIs and not its specialized extension of EntityModel.

We can debate about the finer edges of unit vs. integration testing, but long story short: you can put this into a test case:

@BeforeEach
void setUp() {

	this.mapper = new ObjectMapper();
	this.mapper.registerModule(new Jackson2HalModule());
	this.mapper.setHandlerInstantiator(new Jackson2HalModule.HalHandlerInstantiator(
			new EvoInflectorLinkRelationProvider(), CurieProvider.NONE, MessageResolver.DEFAULTS_ONLY));
	this.mapper.enable(SerializationFeature.INDENT_OUTPUT);

	this.contextualMapper = createMapper(getClass());
}

...and use it to generate JSON for test purposes. Like this:

@Test // #864
void embeddedSpecUsingHalModelBuilder() throws Exception {

	RepresentationModel<?> model = halModel() //
			.embed(halModel() //
					.entity(new Author("Alan Watts", "January 6, 1915", "November 16, 1973")) //
					.link(ALAN_WATTS_SELF) //
					.build(), AUTHOR_REL)
			.embed(halModel() //
					.entity(new Author("John Smith", null, null)) //
					.link(JOHN_SMITH_SELF) //
					.build(), ILLUSTRATOR_REL)
			.link(Link.of("/books/the-way-of-zen")) //
			.link(Link.of("/people/alan-watts", AUTHOR_REL)) //
			.link(Link.of("/people/john-smith", ILLUSTRATOR_REL)) //
			.build();

	assertThat(this.mapper.writeValueAsString(model))
			.isEqualTo(contextualMapper.readFile("hal-embedded-author-illustrator.json"));
}

No need to deal with Mock MVC or spinning up embedded containers. We use this all over the place in Spring HATEOAS for testing.

And considering that we're talking about a library built to serialize and deserialize hypermedia, it frankly makes sense (to me) to verify that serialization actually happened as expected.