Testing Login with espresso is throwing exception

I am trying to test the text of the button is changing while trying to login when the button is pressed. Login button text is actually changing the text to Verifying... when the system is checking the credentials with server and once done, the text changes to LOGIN again. Whenever I am trying to test that with espresso;the UI part is completing assigning values to the edittext and clicked the button, the thread then freezes and few times later it throws an error. As I am new in testing, I would be grateful if you could explain how this problem can be resolved or what is the approach that I should take for this kind of scenarios.

This is my test class.

@LargeTest
@RunWith(AndroidJUnit4.class)
public class LoginTest {
 private String userName;
 private String userPass;
 private LoginIdlingResource idlingResource;
 @Rule
 public ActivityTestRule<LoginActivity> activityRule = new 
 ActivityTestRule<LoginActivity>(LoginActivity.class);
 @Before
 public void assignCredentials (){
    userName = "ABC";
    userPass = "ABC";
 }
 @Before
 public void registerIntentServiceIdlingResource() throws Exception {
    LoginActivity activity = activityRule.getActivity();
    idlingResource = new LoginIdlingResource(activity);
    Espresso.registerIdlingResources(idlingResource);
 }
 @Test
 public void buttonTextChanged(){
    onView(withId(R.id.edittext_user))
            .perform(typeText(userName));
    onView(withId(R.id.edittext_pass))
            .perform(typeText(userPass));
    onView(withId(R.id.submit_login))
            .perform(click());
    onView(withId(R.id.submit_login))
            .check(matches(withText("Verifying...")));
 }
 @After
 public void unregisterIntentServiceIdlingResource() {
    Espresso.unregisterIdlingResources(idlingResource);
 }
}

I have prepared an IdlingResource.

public class LoginIdlingResource implements IdlingResource {
private LoginActivity mActivity;
private ResourceCallback mCallBack;
 public LoginIdlingResource(LoginActivity context){
    mActivity = context;
 }
 @Override
 public String getName() {
    return "LoginActivityIdleName";
 }
 @Override
 public boolean isIdleNow() {
    boolean idle = isIdle();
    if (idle && mCallBack!=null){
        mCallBack.onTransitionToIdle();
    }
    return idle;
 }
 @Override
 public void registerIdleTransitionCallback(ResourceCallback callback) {
    this.mCallBack = callback;
 }
 public boolean isIdle() {
    return mActivity != null && mCallBack != null && 
    !mActivity.isNetworkOperationGoingOn();
 }
}

This is generating the following exception

android.support.test.espresso.PerformException: Error performing 'single 
click - At Coordinates: 539, 903 and precision: 16, 16' on view 'with id: 
com.abc.rt:id/submit_login'.
at android.support.test.espresso.PerformException$Builder.
build(PerformException.java:83)
at android.support.test.espresso.base.DefaultFailureHandler.
getUserFriendlyError(DefaultFailureHandler.java:80)
at android.support.test.espresso.base.DefaultFailureHandler.
handle(DefaultFailureHandler.java:56)
at 
android.support.test.espresso.ViewInteraction.
runSynchronouslyOnUiThread(ViewInteraction.java:184)
at android.support.test.espresso.ViewInteraction.
doPerform(ViewInteraction.java:115)
at android.support.test.espresso.ViewInteraction.
perform(ViewInteraction.java:87)
at com.abc.rt.LoginTest.buttonTextChanged(LoginTest.java:92)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at org.junit.runners.model.FrameworkMethod$1.
runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.
run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.
invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.
evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.
evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.
evaluate(RunAfters.java:27)
at android.support.test.internal.statement.UiThreadStatement.
evaluate(UiThreadStatement.java:55)
at android.support.test.rule.ActivityTestRule$ActivityStatement.
evaluate(ActivityTestRule.java:270)