public static void verifyBody(String expectedBody, URL url) throws InterruptedException {
    Assert.assertEquals(expectedBody, getContent(url));
  }
Verifies the response body. Repeatedly tries {@code url} at the interval of .5 seconds for up
to 20 seconds until getting OK HTTP response code.
jib-plugins-common/src/test/java/com/google/cloud/tools/jib/api/HttpRequestTester.java