Add support for conversion of the whole JSON document

Closes gh-33018

spring-test/src/test/java/org/springframework/test/json/AbstractJsonContentAssertTests.java

@@ -26,9 +26,12 @@ import java.util.Map;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.assertj.core.api.AbstractObjectAssert;
 import org.assertj.core.api.AssertProvider;
 import org.assertj.core.api.InstanceOfAssertFactories;
+import org.assertj.core.api.InstanceOfAssertFactory;
 import org.json.JSONException;
 import org.json.JSONObject;
 import org.junit.jupiter.api.Nested;
@@ -100,6 +103,56 @@ class AbstractJsonContentAssertTests {
 		});
 	}
 
+	@Nested
+	class ConversionTests {
+
+		@Test
+		void convertToTargetType() {
+			assertThat(forJson(SIMPSONS, jsonHttpMessageConverter))
+					.convertTo(Family.class)
+					.satisfies(family -> assertThat(family.familyMembers()).hasSize(5));
+		}
+
+		@Test
+		void convertToIncompatibleTargetTypeShouldFail() {
+			AbstractJsonContentAssert<?> jsonAssert = assertThat(forJson(SIMPSONS, jsonHttpMessageConverter));
+			assertThatExceptionOfType(AssertionError.class)
+					.isThrownBy(() -> jsonAssert.convertTo(Member.class))
+					.withMessageContainingAll("To convert successfully to:",
+							Member.class.getName(), "But it failed:");
+		}
+
+		@Test
+		void convertUsingAssertFactory() {
+			assertThat(forJson(SIMPSONS, jsonHttpMessageConverter))
+					.convertTo(new FamilyAssertFactory())
+					.hasFamilyMember("Homer");
+		}
+
+		private AssertProvider<AbstractJsonContentAssert<?>> forJson(@Nullable String json,
+				@Nullable GenericHttpMessageConverter<Object> jsonHttpMessageConverter) {
+
+			return () -> new TestJsonContentAssert(json, jsonHttpMessageConverter);
+		}
+
+		private static class FamilyAssertFactory extends InstanceOfAssertFactory<Family, FamilyAssert> {
+			public FamilyAssertFactory() {
+				super(Family.class, FamilyAssert::new);
+			}
+		}
+
+		private static class FamilyAssert extends AbstractObjectAssert<FamilyAssert, Family> {
+			public FamilyAssert(Family family) {
+				super(family, FamilyAssert.class);
+			}
+
+			public FamilyAssert hasFamilyMember(String name) {
+				assertThat(this.actual.familyMembers).anySatisfy(m -> assertThat(m.name()).isEqualTo(name));
+				return this.myself;
+			}
+		}
+	}
+
 	@Nested
 	class HasPathTests {
 
@@ -261,14 +314,14 @@ class AbstractJsonContentAssertTests {
 		void convertToWithoutHttpMessageConverterShouldFail() {
 			JsonPathValueAssert path = assertThat(forJson(SIMPSONS)).extractingPath("$.familyMembers[0]");
 			assertThatIllegalStateException()
-					.isThrownBy(() -> path.convertTo(ExtractingPathTests.Member.class))
+					.isThrownBy(() -> path.convertTo(Member.class))
 					.withMessage("No JSON message converter available to convert {name=Homer}");
 		}
 
 		@Test
 		void convertToTargetType() {
 			assertThat(forJson(SIMPSONS, jsonHttpMessageConverter))
-					.extractingPath("$.familyMembers[0]").convertTo(ExtractingPathTests.Member.class)
+					.extractingPath("$.familyMembers[0]").convertTo(Member.class)
 					.satisfies(member -> assertThat(member.name).isEqualTo("Homer"));
 		}
 
@@ -283,7 +336,7 @@ class AbstractJsonContentAssertTests {
 		}
 
 		@Test
-		void convertArrayToParameterizedType() {
+		void convertArrayUsingAssertFactory() {
 			assertThat(forJson(SIMPSONS, jsonHttpMessageConverter))
 					.extractingPath("$.familyMembers")
 					.convertTo(InstanceOfAssertFactories.list(Member.class))
@@ -336,8 +389,6 @@ class AbstractJsonContentAssertTests {
 		}
 
 
-		private record Member(String name) {}
-
 		private record Customer(long id, String username) {}
 
 		private AssertProvider<AbstractJsonContentAssert<?>> forJson(@Nullable String json) {
@@ -836,6 +887,12 @@ class AbstractJsonContentAssertTests {
 		return () -> new TestJsonContentAssert(json, null);
 	}
 
+
+	record Member(String name) {}
+
+	@JsonIgnoreProperties(ignoreUnknown = true)
+	record Family(List<Member> familyMembers) {}
+
 	private static class TestJsonContentAssert extends AbstractJsonContentAssert<TestJsonContentAssert> {
 
 		public TestJsonContentAssert(@Nullable String json, @Nullable GenericHttpMessageConverter<Object> jsonMessageConverter) {