Fix TestHelloWorldAppExample

The test should be checking that the HTTP response *contains* the text "Hello, World" rather than checking for exact equality. It turns out the book itself had the right code in it, but when copying the test code to this repo, I somehow got an old versison of this one test.

Author: brikis98

code/terraform/07-testing-terraform-code/test/hello_world_app_example_test.go

@@ -3,6 +3,7 @@ package test
 import (
 	"fmt"
 	"github.com/gruntwork-io/terratest/modules/random"
+	"strings"
 
 	"github.com/gruntwork-io/terratest/modules/http-helper"
 
@@ -36,19 +37,18 @@ func TestHelloWorldAppExample(t *testing.T)  {
 	albDnsName := terraform.OutputRequired(t, opts, "alb_dns_name")
 	url := fmt.Sprintf("http://%s", albDnsName)
 
-	expectedStatus := 200
-	expectedBody := "Hello, World"
-
 	maxRetries := 10
 	timeBetweenRetries := 10 * time.Second
 
-	http_helper.HttpGetWithRetry(
+	http_helper.HttpGetWithRetryWithCustomValidation(
 		t,
 		url,
-		expectedStatus,
-		expectedBody,
 		maxRetries,
 		timeBetweenRetries,
+		func(status int, body string) bool {
+			return status == 200 &&
+				strings.Contains(body, "Hello, World")
+		},
 	)
 
 }