Polish "Implement DefaultErrorResponseBuilder#headers(Consumer)"

See gh-33156

spring-web/src/test/java/org/springframework/web/ErrorResponseTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.http.HttpStatus;
+
+import static java.util.Map.entry;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ErrorResponse}.
+ *
+ * @author Stephane Nicoll
+ */
+class ErrorResponseTests {
+
+	@Test
+	void createWithHttpHeader() {
+		ErrorResponse response = ErrorResponse.builder(new IllegalStateException(), HttpStatus.BAD_REQUEST, "test")
+				.header("header", "value").build();
+		assertThat(response.getHeaders()).containsOnly(entry("header", List.of("value")));
+	}
+
+	@Test
+	void createWithHttpHeadersConsumer() {
+		ErrorResponse response = ErrorResponse.builder(new IllegalStateException(), HttpStatus.BAD_REQUEST, "test")
+				.header("header", "value")
+				.headers(headers -> {
+					headers.add("header", "value2");
+					headers.add("another", "value3");
+				}).build();
+		assertThat(response.getHeaders()).containsOnly(entry("header", List.of("value", "value2")),
+				entry("another", List.of("value3")));
+	}
+
+}