From 67ace0894b803b06419c42c48e320cb6ac2d8f1f Mon Sep 17 00:00:00 2001
From: Yevgeniy Brikman <brikis98@gmail.com>
Date: Fri, 1 Apr 2016 11:41:14 +0200
Subject: [PATCH 1/2] Fetch the default VPC instead of a random one

We should not be using VPCs at random. Our tests create and destroy
VPCs all the time, so it's possible that one test will accidentally try
to use a VPC that another test is trying to destroy. This changes
terratest to return the default VPC instead of a random one.
---
 aws/vpc.go             | 22 +++++++++++++---------
 rand_resources.go      |  2 +-
 rand_resources_test.go |  2 +-
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/aws/vpc.go b/aws/vpc.go
index f95930a4c..6e2489f17 100644
--- a/aws/vpc.go
+++ b/aws/vpc.go
@@ -1,10 +1,11 @@
 package aws
+
 import (
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/aws"
 	"errors"
-	"github.com/gruntwork-io/terratest/util"
+	"strconv"
 )
 
 var VpcIdFilterName = "vpc-id"
@@ -15,25 +16,28 @@ type Vpc struct {
 	Subnets    []ec2.Subnet	// A list of subnets in the VPC
 }
 
-func GetRandomVpc(awsRegion string) (Vpc, error) {
+var IS_DEFAULT_FILTER_NAME = "isDefault"
+var IS_DEFAULT_FILTER_VALUE = "true"
+
+func GetDefaultVpc(awsRegion string) (Vpc, error) {
 	vpc := Vpc{}
 
 	svc := ec2.New(session.New(), aws.NewConfig().WithRegion(awsRegion))
-	vpcs, err := svc.DescribeVpcs(&ec2.DescribeVpcsInput{})
+	defaultVpcFilter := ec2.Filter{Name: &IS_DEFAULT_FILTER_NAME, Values: []*string{&IS_DEFAULT_FILTER_VALUE}}
+	vpcs, err := svc.DescribeVpcs(&ec2.DescribeVpcsInput{Filters: []*ec2.Filter{&defaultVpcFilter}})
 	if err != nil {
 		return vpc, err
 	}
 
 	numVpcs := len(vpcs.Vpcs)
-	if numVpcs == 0 {
-		return vpc, errors.New("No VPCs found in region " + awsRegion)
+	if numVpcs != 1 {
+		return vpc, errors.New("Expected to find one default VPC in region " + awsRegion + " but found " + strconv.Itoa(numVpcs))
 	}
 
-	randomIndex := util.Random(0, numVpcs)
-	randomVpc := vpcs.Vpcs[randomIndex]
+	defaultVpc := vpcs.Vpcs[0]
 
-	vpc.Id = *randomVpc.VpcId
-	vpc.Name = FindVpcName(randomVpc)
+	vpc.Id = *defaultVpc.VpcId
+	vpc.Name = FindVpcName(defaultVpc)
 
 	vpc.Subnets, err = GetSubnetsForVpc(vpc.Id, awsRegion)
 	return vpc, err
diff --git a/rand_resources.go b/rand_resources.go
index e07cb59ca..c4636d73a 100644
--- a/rand_resources.go
+++ b/rand_resources.go
@@ -101,5 +101,5 @@ func (r *RandomResourceCollection) GetRandomPrivateCidrBlock(prefix int) string
 }
 
 func (r *RandomResourceCollection) GetRandomVpc() (aws.Vpc, error) {
-	return aws.GetRandomVpc(r.AwsRegion)
+	return aws.GetDefaultVpc(r.AwsRegion)
 }
diff --git a/rand_resources_test.go b/rand_resources_test.go
index d174cef14..219a969d9 100644
--- a/rand_resources_test.go
+++ b/rand_resources_test.go
@@ -121,7 +121,7 @@ func TestAllParametersSet(t *testing.T) {
 	}
 }
 
-func TestGetRandomVpc(t *testing.T) {
+func TestGetDefaultVpc(t *testing.T) {
 	t.Parallel()
 
 	ro := NewRandomResourceCollectionOptions()

From 00e565fb03ef3934784a199000cb261e3921a1a5 Mon Sep 17 00:00:00 2001
From: Yevgeniy Brikman <brikis98@gmail.com>
Date: Fri, 1 Apr 2016 11:48:08 +0200
Subject: [PATCH 2/2] Rename API in terratest package too

---
 rand_resources.go      | 2 +-
 rand_resources_test.go | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/rand_resources.go b/rand_resources.go
index c4636d73a..fb0dede1c 100644
--- a/rand_resources.go
+++ b/rand_resources.go
@@ -100,6 +100,6 @@ func (r *RandomResourceCollection) GetRandomPrivateCidrBlock(prefix int) string
 	return util.GetRandomPrivateCidrBlock(prefix)
 }
 
-func (r *RandomResourceCollection) GetRandomVpc() (aws.Vpc, error) {
+func (r *RandomResourceCollection) GetDefaultVpc() (aws.Vpc, error) {
 	return aws.GetDefaultVpc(r.AwsRegion)
 }
diff --git a/rand_resources_test.go b/rand_resources_test.go
index 219a969d9..14ee00ca3 100644
--- a/rand_resources_test.go
+++ b/rand_resources_test.go
@@ -130,7 +130,7 @@ func TestGetDefaultVpc(t *testing.T) {
 		t.Fatalf("Failed to create RandomResourceCollection: %s", err.Error())
 	}
 
-	vpc, err := rand.GetRandomVpc()
+	vpc, err := rand.GetDefaultVpc()
 	if err != nil {
 		t.Fatalf("Failed to get random VPC: %s", err.Error())
 	}