diff --git a/test/functional/mempool_persist.py b/test/functional/mempool_persist.py
--- a/test/functional/mempool_persist.py
+++ b/test/functional/mempool_persist.py
@@ -81,7 +81,8 @@
         self.stop_nodes()
         # Give this one a head-start, so we can be "extra-sure" that it didn't
         # load anything later
-        self.start_node(1)
+        # Also don't store the mempool, to keep the datadir clean
+        self.start_node(1, extra_args=["-persistmempool=0"])
         self.start_node(0)
         self.start_node(2)
         wait_until(lambda: self.nodes[0].getmempoolinfo()["loaded"], timeout=1)
diff --git a/test/functional/test_framework/netutil.py b/test/functional/test_framework/netutil.py
--- a/test/functional/test_framework/netutil.py
+++ b/test/functional/test_framework/netutil.py
@@ -9,7 +9,6 @@
 
 import array
 from binascii import unhexlify
-import fcntl
 import os
 import socket
 import struct
@@ -99,6 +98,9 @@
     '''
     Return all interfaces that are up
     '''
+    # Linux only, so only import when required
+    import fcntl
+
     is_64bits = sys.maxsize > 2**32
     struct_size = 40 if is_64bits else 32
     s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
diff --git a/test/functional/wallet_dump.py b/test/functional/wallet_dump.py
--- a/test/functional/wallet_dump.py
+++ b/test/functional/wallet_dump.py
@@ -7,7 +7,10 @@
 import os
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+)
 
 
 def read_dump(file_name, addrs, script_addrs, hd_master_addr_old):
@@ -88,7 +91,10 @@
         self.start_nodes()
 
     def run_test(self):
-        tmpdir = self.options.tmpdir
+        wallet_unenc_dump = os.path.join(
+            self.nodes[0].datadir, "wallet.unencrypted.dump")
+        wallet_enc_dump = os.path.join(
+            self.nodes[0].datadir, "wallet.encrypted.dump")
 
         # generate 20 addresses to compare against the dump
         test_addr_count = 20
@@ -106,14 +112,11 @@
             1, [addrs[0]["address"]])["address"]
 
         # dump unencrypted wallet
-        result = self.nodes[0].dumpwallet(
-            tmpdir + "/node0/wallet.unencrypted.dump")
-        assert_equal(result['filename'], os.path.abspath(
-            tmpdir + "/node0/wallet.unencrypted.dump"))
+        result = self.nodes[0].dumpwallet(wallet_unenc_dump)
+        assert_equal(result['filename'], wallet_unenc_dump)
 
         found_addr, found_script_addr, found_addr_chg, found_addr_rsv, hd_master_addr_unenc = \
-            read_dump(tmpdir + "/node0/wallet.unencrypted.dump",
-                      addrs, [multisig_addr], None)
+            read_dump(wallet_unenc_dump, addrs, [multisig_addr], None)
         # all keys must be in the dump
         assert_equal(found_addr, test_addr_count)
         # all scripts must be in the dump
@@ -128,11 +131,14 @@
         self.nodes[0].walletpassphrase('test', 10)
         # Should be a no-op:
         self.nodes[0].keypoolrefill()
-        self.nodes[0].dumpwallet(tmpdir + "/node0/wallet.encrypted.dump")
+        self.nodes[0].dumpwallet(wallet_enc_dump)
 
         found_addr, found_script_addr, found_addr_chg, found_addr_rsv, _ = \
-            read_dump(tmpdir + "/node0/wallet.encrypted.dump",
-                      addrs, [multisig_addr], hd_master_addr_unenc)
+            read_dump(
+                wallet_enc_dump,
+                addrs,
+                [multisig_addr],
+                hd_master_addr_unenc)
         assert_equal(found_addr, test_addr_count)
         assert_equal(found_script_addr, 1)
         # old reserve keys are marked as change now
@@ -140,8 +146,9 @@
         assert_equal(found_addr_rsv, 90 * 2)
 
         # Overwriting should fail
-        assert_raises_rpc_error(-8, "already exists",
-                                self.nodes[0].dumpwallet, tmpdir + "/node0/wallet.unencrypted.dump")
+        assert_raises_rpc_error(-8,
+                                "already exists",
+                                lambda: self.nodes[0].dumpwallet(wallet_enc_dump))
 
         # Restart node with new wallet, and test importwallet
         self.stop_node(0)
@@ -151,8 +158,7 @@
         result = self.nodes[0].getaddressinfo(multisig_addr)
         assert result['ismine'] is False
 
-        self.nodes[0].importwallet(os.path.abspath(
-            tmpdir + "/node0/wallet.unencrypted.dump"))
+        self.nodes[0].importwallet(wallet_unenc_dump)
 
         # Now check IsMine is true
         result = self.nodes[0].getaddressinfo(multisig_addr)