Add EFS mount target DNS helper function.

Signed-off-by: Krzysztof Wilczynski <[email protected]>

builtin/providers/aws/resource_aws_efs_mount_target.go

@@ -205,7 +205,7 @@ func resourceAwsEfsMountTargetRead(d *schema.ResourceData, meta interface{}) err
 	}
 
 	region := meta.(*AWSClient).region
-	err = d.Set("dns_name", fmt.Sprintf("%s.%s.efs.%s.amazonaws.com", az, *mt.FileSystemId, region))
+	err = d.Set("dns_name", resourceAwsEfsMountTargetDnsName(az, *mt.FileSystemId, region))
 	if err != nil {
 		return err
 	}
@@ -284,3 +284,7 @@ func resourceAwsEfsMountTargetDelete(d *schema.ResourceData, meta interface{}) e
 
 	return nil
 }
+
+func resourceAwsEfsMountTargetDnsName(az, fileSystemId, region string) string {
+	return fmt.Sprintf("%s.%s.efs.%s.amazonaws.com", az, fileSystemId, region)
+}

builtin/providers/aws/resource_aws_efs_mount_target_test.go

@@ -57,6 +57,17 @@ func TestAccAWSEFSMountTarget_basic(t *testing.T) {
 	})
 }
 
+func TestResourceAWSEFSMountTarget_dnsName(t *testing.T) {
+	actual := resourceAwsEfsMountTargetDnsName("non-existant-1c",
+		"fs-123456ab", "non-existant-1")
+
+	expected := "non-existant-1c.fs-123456ab.efs.non-existant-1.amazonaws.com"
+	if actual != expected {
+		t.Fatalf("Expected EFS mount target DNS name to be %s, got %s",
+			expected, actual)
+	}
+}
+
 func testAccCheckEfsMountTargetDestroy(s *terraform.State) error {
 	conn := testAccProvider.Meta().(*AWSClient).efsconn
 	for _, rs := range s.RootModule().Resources {