Introduce failing tests for HttpHeaders

See gh-22821

Author: sbrannen

spring-web/src/test/java/org/springframework/http/HttpHeadersTests.java

@@ -36,6 +36,7 @@
 import java.util.TimeZone;
 
 import org.hamcrest.Matchers;
+import org.junit.Ignore;
 import org.junit.Test;
 
 import static org.hamcrest.Matchers.*;
@@ -559,6 +560,36 @@ public void bearerAuth() {
 		assertEquals("Bearer foo", authorization);
 	}
 
+	@Test
+	@Ignore("Disabled until gh-22821 is resolved")
+	public void removalFromKeySetRemovesEntryFromUnderlyingMap() {
+		String headerName = "MyHeader";
+		String headerValue = "value";
+
+		assertTrue(headers.isEmpty());
+		headers.add(headerName, headerValue);
+		assertTrue(headers.containsKey(headerName));
+		headers.keySet().removeIf(key -> key.equals(headerName));
+		assertTrue(headers.isEmpty());
+		headers.add(headerName, headerValue);
+		assertEquals(headerValue, headers.get(headerName));
+	}
+
+	@Test
+	@Ignore("Disabled until gh-22821 is resolved")
+	public void removalFromEntrySetRemovesEntryFromUnderlyingMap() {
+		String headerName = "MyHeader";
+		String headerValue = "value";
+
+		assertTrue(headers.isEmpty());
+		headers.add(headerName, headerValue);
+		assertTrue(headers.containsKey(headerName));
+		headers.entrySet().removeIf(entry -> entry.getKey().equals(headerName));
+		assertTrue(headers.isEmpty());
+		headers.add(headerName, headerValue);
+		assertEquals(headerValue, headers.get(headerName));
+	}
+
 	@Test
 	public void readOnlyHttpHeadersRetainEntrySetOrder() {
 		headers.add("aardvark", "enigma");