import org.junit.Before;
import org.junit.Test;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

import java.net.URI;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.CompletableFuture;
import java.util.stream.IntStream;

import static org.junit.Assert.*;

public class CompletableFutureTest {

    private Collection<CompletableFuture<Void>> futures;

    private Collection<ResponseEntity<String>> results;

    private final RestTemplate restTemplate = new RestTemplate();

    @Before
    public void setup() {
        this.futures = new ArrayList<>();
        this.results = new ArrayList<>();
    }

    @Test
    public void asyncHttpCallsTest() {
        IntStream.range(0, 20).forEach(i -> {
            this.futures.add(CompletableFuture.runAsync(() -> {
                this.results.add(this.restTemplate.getForEntity(URI.create("http://www.google.com"), String.class));
            }));
        });

        this.futures.forEach(CompletableFuture::join);

        Assert.assertEquals(20, this.results.size());
    }

}