This is a test to show how to use expresso to check if a toast was displayed.

ApplicationTest.java

package com.github.brunodles.toastespresso;

import android.support.test.rule.ActivityTestRule;
import android.support.test.runner.AndroidJUnit4;
import android.test.suitebuilder.annotation.LargeTest;

import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.action.ViewActions.click;
import static android.support.test.espresso.assertion.ViewAssertions.matches;
import static android.support.test.espresso.matcher.RootMatchers.withDecorView;
import static android.support.test.espresso.matcher.ViewMatchers.isDisplayed;
import static android.support.test.espresso.matcher.ViewMatchers.withText;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.not;

@RunWith(AndroidJUnit4.class)
@LargeTest
public class ApplicationTest {

    @Rule
    public ActivityTestRule<MainActivity> mActivityRule = new ActivityTestRule(MainActivity.class);

    @Test
    public void shouldShowToast() {
        onView(withText("Click on this button")).perform(click());
        onView(withText(R.string.toast)).inRoot(withDecorView(not(is(mActivityRule.getActivity().getWindow().getDecorView())))).check(matches(isDisplayed()));
    }


}