add validation for target name

moto/elbv2/exceptions.py

@@ -170,7 +170,7 @@ class DuplicatePriorityError(ELBClientError):
 
 class InvalidTargetGroupNameError(ELBClientError):
 
-    def __init__(self, invalid_name):
+    def __init__(self, msg):
         super(InvalidTargetGroupNameError, self).__init__(
-            "ValidationError",
-            "Target group name '%s' cannot be longer than '32' characters" % invalid_name)
+            "ValidationError", msg
+        )

moto/elbv2/models.py

@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 import datetime
+import re
 from moto.compat import OrderedDict
 from moto.core import BaseBackend, BaseModel
 from moto.ec2.models import ec2_backends
@@ -266,7 +267,24 @@ class ELBv2Backend(BaseBackend):
 
     def create_target_group(self, name, **kwargs):
         if len(name) > 32:
-            raise InvalidTargetGroupNameError(name)
+            raise InvalidTargetGroupNameError(
+                "Target group name '%s' cannot be longer than '32' characters" % name
+            )
+        if not re.match('^[a-zA-Z0-9\-]+$', name):
+            raise InvalidTargetGroupNameError(
+                "Target group name '%s' can only contain characters that are alphanumeric characters or hyphens(-)" % name
+            )
+
+        # undocumented validation
+        if not re.match('(?!.*--)(?!^-)(?!.*-$)^[A-Za-z0-9-]+$', name):
+            raise InvalidTargetGroupNameError(
+                "1 validation error detected: Value '%s' at 'targetGroup.targetGroupArn.targetGroupName' failed to satisfy constraint: Member must satisfy regular expression pattern: (?!.*--)(?!^-)(?!.*-$)^[A-Za-z0-9-]+$" % name
+            )
+
+        if name.startswith('-') or name.endswith('-'):
+            raise InvalidTargetGroupNameError(
+                "Target group name '%s' cannot begin or end with '-'" % name
+            )
         for target_group in self.target_groups.values():
             if target_group.name == name:
                 raise DuplicateTargetGroupName()