How do I get Jersey Test/Client to not fill in a d

I'm trying to handle a request with no Accept header in a particular way, but Jersey seems hell-bent on filling one in, no matter what I do, so it always looks like the request has an Accept header, even if it doesn't.

import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.JerseyTest;
import org.junit.Test;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;

import static org.junit.Assert.assertEquals;

public class JerseyTestTest extends JerseyTest {

    @Path("hello")
    public static class HelloResource {
        @GET
        public String getHello(@Context HttpHeaders httpHeaders) {
            String acceptHeader = httpHeaders.getHeaderString(HttpHeaders.ACCEPT);
            return acceptHeader != null ? acceptHeader : "No Accept Header";
        }
    }

    @Override
    protected Application configure() {
        return new ResourceConfig(HelloResource.class);
    }

    @Test
    public void test() {
        final String hello = target("hello").request()
                .header(HttpHeaders.ACCEPT, null) // null means remove header
                .get(String.class);
        assertEquals("No Accept Header", hello);
    }
}

This test results in:

org.junit.ComparisonFailure: 
Expected :No Accept Header
Actual   :text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2

Somehow there is a default Accept header of text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2 that gets set somewhere. It's not documented, and I would love to figure out how to disable it. I've looked through the Jersey source, but can't seem to locate where this is happening or why.

Update: when I use curl to hit an endpoint without an Accept header, there is no generated Accept header, so the problem lies in Jersey Client or the Jersey Test environment, somehow.

Update 2: This bug exhibits when using the default Grizzly2 test container or the JDK test container, but NOT with the In Memory test container.

Not sure if this helps anyone else but we were seeing similar behavior calling a service in production with our client code. We are using Jersey 2.21.1.

Expanded the code from the original post and found the following to be true:

if Accept header is null then Jersey adds the default
if Accept header is an empty String then an empty Accept header is used
if Accept header has a value it is used

I'm not sure if there is a way to tell Jersey not to add the default value when a null is used.

public class JerseyAcceptHeaderTest extends JerseyTest {

    @Path("hello")
    public static class HelloResource {
        @GET
        public String getHello(@Context HttpHeaders httpHeaders) {
            String acceptHeader = httpHeaders.getHeaderString(HttpHeaders.ACCEPT);
            System.out.println("SERVER RECEIVED:" + acceptHeader);

            if (acceptHeader == null) {
                return "Null Accept Header";
            } else if (acceptHeader.equals("")) {
                return "No Accept Header";
            } else {
                return acceptHeader;
            }
        }
    }

    @Override
    protected Application configure() {
        return new ResourceConfig(HelloResource.class);
    }

    /**
     * this seems to be a bug in Jersey
     * it overrides a null Accept header
     */
    @Test
    public void test_accept_header_with_null() {
        final String acceptHeader = target("hello").request()
                .header(HttpHeaders.ACCEPT, null)
                .get(String.class);
        assertEquals("Null Accept Header", acceptHeader);
    }

    @Test
    public void test_accept_header_with_empty_string() {
        final String acceptHeader = target("hello").request()
                .header(HttpHeaders.ACCEPT, "")
                .get(String.class);
        assertEquals("No Accept Header", acceptHeader);
    }

    @Test
    public void test_accept_header_with_spaced_string() {
        final String acceptHeader = target("hello").request()
                .header(HttpHeaders.ACCEPT, "  ")
                .get(String.class);
        assertEquals("No Accept Header", acceptHeader);
    }

    @Test
    public void test_accept_header_with_value() {
        final String acceptHeader = target("hello").request()
                .header(HttpHeaders.ACCEPT, "application/json")
                .get(String.class);
        assertEquals("application/json", acceptHeader);
    }

}