Improve random_string util function

When writing new test, I find myself constantly computing the
size from desired strength and prefix length, whereas I mostly
don't care about the final size at all (plus, one can usually
see that from surrounding code).

Providing strength simplifies use and the function code.

3 files changed, 9 insertions, 7 deletions

diff --git a/src/account/test/TestAccountRaceConditions.py b/src/account/test/TestAccountRaceConditions.py
index 6125bd3..61785c8 100644
--- a/src/account/test/TestAccountRaceConditions.py
+++ b/src/account/test/TestAccountRaceConditions.py
@@ -123,7 +123,7 @@ class TestAccountRaceConditions(AccountBase):
     def setUp(self):
         self.user_count = 20        # = thread count
         self.prefix = "user"
-        self.names = [methods.random_string(size=8, prefix=self.prefix)
+        self.names = [methods.random_string(strength=8, prefix=self.prefix)
                       for i in xrange(self.user_count)]
 
         self.bs = BackupStorage()
diff --git a/src/account/test/common.py b/src/account/test/common.py
index 862d1d4..8f3eeba 100644
--- a/src/account/test/common.py
+++ b/src/account/test/common.py
@@ -271,11 +271,11 @@ class BaseCrippler:
 
     def _random_binary(self, size=BINARY_LENGTH):
         chars = ''.join([chr(i) for i in xrange(256)])
-        return methods.random_string(size, chars)
+        return methods.random_string(strength=size, chars=chars)
 
     def _random_line(self, size=LINE_LENGTH):
         chars = string.letters + string.punctuation + " \t"
-        return methods.random_string(size, chars) + "\n"
+        return methods.random_string(strength=size, chars=chars) + "\n"
 
     def _random_lines(self, size=LINE_LENGTH, count=LINE_COUNT):
         return "".join([self._random_line(size) for i in xrange(count)])
diff --git a/src/account/test/methods.py b/src/account/test/methods.py
index 9c033c5..4043ddf 100644
--- a/src/account/test/methods.py
+++ b/src/account/test/methods.py
@@ -97,15 +97,17 @@ def create_group(group_name):
     if not group_exists(group_name):
         subprocess.check_call(["groupadd", group_name])
 
-def random_string(size=6, chars=None, prefix=""):
+def random_string(strength=6, chars=None, prefix=""):
     """
     Generate a random string, e.g. usable as UID/GID
+
+    strength is count of random characters in the final string.  chars
+    is sequence of characters to choose from, and prefix can be provided
+    to prepend it to final string.
     """
     if chars is None:
         chars = string.ascii_uppercase + string.digits
-    if len(prefix) > size:
-        raise ValueError("prefix too long: %s > %s" % (len(prefix), size))
-    salt = ''.join([random.choice(chars) for x in range(size - len(prefix))])
+    salt = ''.join([random.choice(chars) for x in range(strength)])
     return prefix + salt
 
 def random_shell():