Remove HttpHeaders#asMultiValueMap usages from Kotlin tests

Closes gh-34327

spring-web/src/test/kotlin/org/springframework/http/converter/cbor/KotlinSerializationCborHttpMessageConverterTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -170,8 +170,7 @@ class KotlinSerializationCborHttpMessageConverterTests {
 
 		this.converter.write(serializableBean, null, outputMessage)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/cbor"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/cbor")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -182,8 +181,7 @@ class KotlinSerializationCborHttpMessageConverterTests {
 
 		this.converter.write(serializableBean, null, outputMessage)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/cbor"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/cbor")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -193,8 +191,7 @@ class KotlinSerializationCborHttpMessageConverterTests {
 
 		this.converter.write(serializableBeanArray, null, outputMessage)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/cbor"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/cbor")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -205,8 +202,7 @@ class KotlinSerializationCborHttpMessageConverterTests {
 
 		this.converter.write(listOf(serializableBean), ResolvableType.forType(typeOf<List<SerializableBean>>().javaType), null, outputMessage, null)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/cbor"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/cbor")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 

spring-web/src/test/kotlin/org/springframework/http/converter/json/KotlinSerializationJsonHttpMessageConverterTests.kt

@@ -255,8 +255,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result)
 				.contains("\"bytes\":[1,2]")
 				.contains("\"array\":[\"Foo\",\"Bar\"]")
@@ -275,8 +274,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result)
 				.contains("\"bytes\":[1,2]")
 				.contains("\"array\":[\"Foo\",\"Bar\"]")
@@ -298,8 +296,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result).isEqualTo(expectedJson)
 	}
 
@@ -317,8 +314,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result).isEqualTo(expectedJson)
 	}
 
@@ -332,8 +328,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_16BE)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf(contentType.toString()))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", contentType.toString())).isTrue()
 		assertThat(result).isEqualTo("\"H\u00e9llo W\u00f6rld\"")
 	}
 
@@ -369,8 +364,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result).isEqualTo("1.0")
 	}
 
@@ -387,8 +381,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result).isEqualTo(expectedJson)
 	}
 
@@ -401,8 +394,7 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 		this.converter.write(value, ResolvableType.forMethodParameter(methodParameter), null, outputMessage, null)
 		val result = outputMessage.getBodyAsString(StandardCharsets.UTF_8)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/json"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/json")).isTrue()
 		assertThat(result).isEqualTo("42")
 	}
 

spring-web/src/test/kotlin/org/springframework/http/converter/protobuf/KotlinSerializationProtobufHttpMessageConverterTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -186,8 +186,7 @@ class KotlinSerializationProtobufHttpMessageConverterTests {
 
 		this.converter.write(serializableBean, null, outputMessage)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/x-protobuf"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/x-protobuf")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -197,9 +196,7 @@ class KotlinSerializationProtobufHttpMessageConverterTests {
 		val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, null, true, 42.0f)
 
 		this.converter.write(serializableBean, null, outputMessage)
-
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/x-protobuf"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/x-protobuf")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -209,8 +206,7 @@ class KotlinSerializationProtobufHttpMessageConverterTests {
 
 		this.converter.write(serializableBeanArray, null, outputMessage)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/x-protobuf"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/x-protobuf")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}
 
@@ -221,8 +217,7 @@ class KotlinSerializationProtobufHttpMessageConverterTests {
 
 		this.converter.write(listOf(serializableBean), ResolvableType.forType(typeOf<List<SerializableBean>>().javaType), null, outputMessage, null)
 
-		@Suppress("DEPRECATION")
-		assertThat(outputMessage.headers.asMultiValueMap()).containsEntry("Content-Type", listOf("application/x-protobuf"))
+		assertThat(outputMessage.headers.containsHeaderValue("Content-Type", "application/x-protobuf")).isTrue()
 		assertThat(outputMessage.bodyAsBytes.isNotEmpty()).isTrue()
 	}