Java Mockito.verify.update Can't not copy enum data

I tried to run unit test but I got an error.

I think this error is related in Mockito.verify.update and enum data because ArgumentCaptor instance copies other data normally.

Here is error message.

2016-04-04 17:15:26.850  INFO 1399 --- [           main] c.p.a.c.a.ConferenceRoleControllerTest   : Started ConferenceRoleControllerTest in 13.768 seconds (JVM running for 14.921)
2016-04-04 17:15:27.136 DEBUG 1399 --- [           main] c.p.a.c.api.ConferenceRoleController     : [API] Creating a new conferenceRole with information:    
com.pjwards.aide.domain.ConferenceRole@7bfcc108[id=1,conferenceRole=<null>,userSet=<null>,conferenceSet=<null>]
[com.pjwards.aide.domain.ConferenceRole@7bfcc108[id=1,conferenceRole=<null>,userSet=<null>,conferenceSet=<null>]]

java.lang.AssertionError: 
Expected: is <ADMIN>
   but: was null
Expected :is <ADMIN>
 Actual   :null
<Click to see difference>


at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:8)
at com.pjwards.aide.controller.api.ConferenceRoleControllerTest.testCreate_NewConferenceRole_ShouldAddConferenceRoleReturnAddedConferenceRole(ConferenceRoleControllerTest.java:111)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

And this is My code: Part of Controller test

@Test
public void  
testUpdate_ConferenceRoleFound_ShouldUpdateConferenceRoleAndReturnIt() throws Exception {
    ConferenceRole updated = new ConferenceRoleBuilder()
            .id(1L)
            .conferenceRole(ROLE)
            .build();

    when(conferenceRoleService.update(any(ConferenceRole.class))).thenReturn(updated);

    mockMvc.perform(put("/api/conference-roles/{id}", 1L)
            .contentType(TestUtil.APPLICATION_JSON_UTF8)
            .content(TestUtil.convertObjectToJsonBytes(updated))
    )
            .andExpect(status().isOk())
            .andExpect(content().contentType(TestUtil.APPLICATION_JSON_UTF8))
            .andExpect(jsonPath("$.message", is("ConferenceRole updated successfully")))
            .andExpect(jsonPath("$.conferenceRole.id", is(1)))
            .andExpect(jsonPath("$.conferenceRole.role", is(ROLE.toString())));

    ArgumentCaptor<ConferenceRole> conferenceRoleArgumentCaptor = ArgumentCaptor.forClass(ConferenceRole.class);
    verify(conferenceRoleService, times(1)).update(conferenceRoleArgumentCaptor.capture());
    verifyNoMoreInteractions(conferenceRoleService);

    ConferenceRole conferenceRoleArgument = conferenceRoleArgumentCaptor.getValue();
    assertThat(conferenceRoleArgument.getId(), is(1L));
    assertThat(conferenceRoleArgument.getRole(), is(updated.getRole()));
}

enum class:

public enum Role {
PARTICIPANT{
    @Override
    public String toString(){
        return "PARTICIPANT";
    }
}, HOST{
    @Override
    public String toString(){
        return "HOST";
    }
}, MANAGER{
    @Override
    public String toString(){
        return "MANAGER";
    }
}, SPEAKER{
    @Override
    public String toString(){
        return "SPEAKER";
    }
}, ADMIN{
    @Override
    public String toString(){
        return "ADMIN";
    }
}, USER{
    @Override
    public String toString(){
        return "USER";
    }
}
}

ConferenceRole code:

@Entity
public class ConferenceRole {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Column(nullable = false)
@Enumerated(EnumType.STRING)
private Role conferenceRole;

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "USER_ROLE",
        joinColumns = @JoinColumn(name = "CONFERENCE_ROLE_ID_FRK"),
        inverseJoinColumns = @JoinColumn(name = "USER_ID_FRK")
)
private Set<User> userSet;

@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "CONFERENCE_CONFERENCE_ROLE",
        joinColumns = @JoinColumn(name = "CONFERENCE_ROLE_ID_FRK"),
        inverseJoinColumns = @JoinColumn(name = "CONFERENCE_ID_FRK")
)
private Set<Conference> conferenceSet;

public Long getId() {
    return id;
}

public Role getRole() {
    return conferenceRole;
}

public Set<User> getUserSet() {
    return userSet;
}

public Set<Conference> getConferenceSet() {
    return conferenceSet;
}

public ConferenceRole(){

}

public ConferenceRole(Role conferenceRole){
    this.conferenceRole = conferenceRole;
}

public void update(Role conferenceRole){
    this.conferenceRole = conferenceRole;
}

public static class Builder {
    private ConferenceRole built;

    public Builder(Role conferenceRole) {
        built = new ConferenceRole();
        built.conferenceRole = conferenceRole;
    }

    public Builder id(Long id) {
        built.id = id;
        return this;
    }

    public Builder user(Set<User> userSet){
        built.userSet = userSet;
        return this;
    }

    public Builder conference(Set<Conference> conferenceSet){
        built.conferenceSet = conferenceSet;
        return this;
    }

    public ConferenceRole build() {
        return built;
    }
}

@Override
public String toString() {
    return ToStringBuilder.reflectionToString(this);
}
}

Please help me....