diff --git a/test/functional/test_framework/util.py b/test/functional/test_framework/util.py
index 3175872b00..1c254b6755 100644
--- a/test/functional/test_framework/util.py
+++ b/test/functional/test_framework/util.py
@@ -25,6 +25,13 @@ logger = logging.getLogger("TestFramework.utils")
 # Assert functions
 ##################
 
+def assert_approx(v, vexp, vspan=0.00001):
+    """Assert that `v` is within `vspan` of `vexp`"""
+    if v < vexp - vspan:
+        raise AssertionError("%s < [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
+    if v > vexp + vspan:
+        raise AssertionError("%s > [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
+
 def assert_fee_amount(fee, tx_size, fee_per_kB):
     """Assert the fee was in range"""
     target_fee = round(tx_size * fee_per_kB / 1000, 8)
diff --git a/test/functional/wallet_avoidreuse.py b/test/functional/wallet_avoidreuse.py
index e3aa6705e5..3c8064ea2d 100755
--- a/test/functional/wallet_avoidreuse.py
+++ b/test/functional/wallet_avoidreuse.py
@@ -6,18 +6,12 @@
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
+    assert_approx,
     assert_equal,
     assert_raises_rpc_error,
     connect_nodes,
 )
 
-# TODO: Copied from wallet_groups.py -- should perhaps move into util.py
-def assert_approx(v, vexp, vspan=0.00001):
-    if v < vexp - vspan:
-        raise AssertionError("%s < [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
-    if v > vexp + vspan:
-        raise AssertionError("%s > [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
-
 def reset_balance(node, discardaddr):
     '''Throw away all owned coins by the node so it gets a balance of 0.'''
     balance = node.getbalance(avoid_reuse=False)
diff --git a/test/functional/wallet_groups.py b/test/functional/wallet_groups.py
index 5452433acf..d1178611bd 100755
--- a/test/functional/wallet_groups.py
+++ b/test/functional/wallet_groups.py
@@ -7,15 +7,10 @@
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.messages import CTransaction, FromHex, ToHex
 from test_framework.util import (
+    assert_approx,
     assert_equal,
 )
 
-def assert_approx(v, vexp, vspan=0.00001):
-    if v < vexp - vspan:
-        raise AssertionError("%s < [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
-    if v > vexp + vspan:
-        raise AssertionError("%s > [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
-
 class WalletGroupTest(BitcoinTestFramework):
     def set_test_params(self):
         self.setup_clean_chain = True