Migrates test to assertJ

Fixes gh-1676

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/test/RouteConstructionIntegrationTests.java

@@ -16,8 +16,6 @@
 
 package org.springframework.cloud.gateway.test;
 
-import org.junit.Assert;
-import org.junit.Ignore;
 import org.junit.Test;
 
 import org.springframework.boot.SpringBootConfiguration;
@@ -27,16 +25,15 @@ import org.springframework.cloud.gateway.filter.GatewayFilter;
 import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
 import org.springframework.context.annotation.Bean;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
 public class RouteConstructionIntegrationTests {
 
 	@Test
-	@Ignore // FIXME: https://github.com/spring-cloud/spring-cloud-gateway/issues/1676
 	public void routesWithVerificationShouldFail() {
-		Assert.assertThrows("java.lang.AssertionError: Stop right now!", Throwable.class,
-				() -> {
-					new SpringApplicationBuilder(TestConfig.class)
-							.profiles("verification-route").run();
-				});
+		assertThatThrownBy(() -> new SpringApplicationBuilder(TestConfig.class)
+				.profiles("verification-route").run())
+						.hasMessageContaining("Stop right now!");
 	}
 
 	@EnableAutoConfiguration