WebTestClient does not provide Hamcrest Matcher assertions for JSONPath [SPR-16729]

[spring-projects-issues]

Eric Deandrea opened SPR-16729 and commented

Seems that the reactive WebTestClient is missing some valuable assertions that are available on MockMvc.

With MockMvc I can do things like

this.mockMvc.perform(get("/some/url"))
  .andExpect(jsonPath("$.someNestedObject.*", Matchers.hasSize(5)))
  .andExpect(jsonPath("$.someNestedObject.anotherObject").value(Matchers.startsWith("Some String")));

The WebTestClient.jsonPath method doesn't have an overloaded

jsonPath(String expression, Matcher<T> matcher)

method like its MockMvcResultMatchers counterpart does. Also JsonPathAssertions doesn't have an overloaded

value(Matcher<T> matcher)

method like its JsonPathResultMatchers counterpart does. Under the covers both JsonPathResultMatchers & JsonPathAssertions utilize the exact same JsonPathExpectationsHelper which exposes the

public <T> void assertValue(String content, Matcher<T> matcher)

method which is needed.

Is there a particular reason this is missing or is it an oversight? Also seems that there is 0 support for assertions against XML using WebTestClient. Again, is there a specific reason as to why not?

---

Affects: 5.0.5

Issue Links:

• Better support for testing JSON [SPR-16737] #21278 Better support for testing JSON
• Provide XML-based assertions in WebTestClient [SPR-16741] #21282 Provide XML-based assertions in WebTestClient
• Introduce consumeWith() methods in WebTestClient assertions [SPR-16574] #21116 Introduce consumeWith() methods in WebTestClient assertions

Referenced from: commits 20de500

[spring-projects-issues]

Eric Deandrea commented

I think this would solve the need:

In org.springframework.test.web.reactive.server.JsonPathAssertions:

/**
 * Applies {@link JsonPathExpectationsHelper#assertValue(String, Matcher)}
 */
public <T> WebTestClient.BodyContentSpec matches(Matcher<T> matcher) {
	this.pathHelper.assertValue(this.content, matcher);
	return this.bodySpec;
}

In org.springframework.test.web.reactive.server.samples:

@Test
public void jsonPathMatches() {
	this.client.get().uri("/persons")
			.accept(MediaType.APPLICATION_JSON_UTF8)
			.exchange()
			.expectStatus().isOk()
			.expectBody()
			.jsonPath("$[*]").matches(Matchers.hasSize(3))
			.jsonPath("$[0].name").matches(Matchers.is("Jane"))
			.jsonPath("$[1].name").matches(Matchers.is("Jason"))
			.jsonPath("$[2].name").matches(Matchers.is("John"));
	}

[spring-projects-issues]

Eric Deandrea commented

I submitted #1794 for this.

[spring-projects-issues]

Rossen Stoyanchev commented

Unlike MockMvc, the WebTestClient does not have expose Hamcrest by choice. There are lots of ways and libraries to assert with. For example Spring Boot favors the more fluent AssertJ style. The idea is to try and provide a core set of built-in options, but otherwise get out of the way and expose the underlying data via java.util.function.Consumer callbacks, so that can be used with any assertion library.

One option would be to expose Consumer-based methods for the values from a JSONPath on JsonPathAssertions, e.g.stringValue(Consumer<String>), booleanValue(Consumer<Boolean>), arrayValue(Consumer<List<?>> consumer), etc. However since many JSON paths may be evaluated, this could be too repetitive.

A probably better option would be to update the underlying JsonPathAssertionsHelper to expose a more fluent API, so it can be used directly, e.g. via Consumer method for the whole body, like this:

this.client.get().uri("/persons")
        .accept(MediaType.APPLICATION_JSON_UTF8)
        .exchange()
        .expectStatus().isOk()
        .expectBody()
        .consumeWith(result -> {
            // use fluent API based on JsonPathExpectationsHelper here..
        });

In addition to that, we could add a few more built-in methods on JSONPath assertions to make it more useful.

[spring-projects-issues]

Eric Deandrea commented

Whatever we do here we also need to support XPath-based assertions, so just exposing the JsonPathExpectationsHelper isn't enough....

See #21282

[spring-projects-issues]

Rossen Stoyanchev commented

Yes the two are related. I just didn't get a chance to comment there yet.

[spring-projects-issues]

Rossen Stoyanchev commented

Related discussion for AssertJ-style assertions in #21278.