diff --git a/tests/fixtures.py b/tests/fixtures.py
index 004a0b03..e69a837b 100644
--- a/tests/fixtures.py
+++ b/tests/fixtures.py
@@ -1,9 +1,11 @@
 from datasette.app import Datasette
+from sanic.testing import PORT as PORT_BASE, SanicTestClient
 import itertools
 import json
 import os
 import pytest
 import random
+import re
 import sqlite3
 import sys
 import string
@@ -11,7 +13,7 @@ import tempfile
 import time
 
 
-class TestClient:
+class MyTestClient:
     def __init__(self, sanic_test_client):
         self.sanic_test_client = sanic_test_client
 
@@ -24,7 +26,7 @@ class TestClient:
 
 
 @pytest.fixture(scope='session')
-def app_client(sql_time_limit_ms=None, max_returned_rows=None, config=None, filename="fixtures.db"):
+def app_client(worker_id, sql_time_limit_ms=None, max_returned_rows=None, config=None, filename="fixtures.db"):
     with tempfile.TemporaryDirectory() as tmpdir:
         filepath = os.path.join(tmpdir, filename)
         conn = sqlite3.connect(filepath)
@@ -49,38 +51,51 @@ def app_client(sql_time_limit_ms=None, max_returned_rows=None, config=None, file
         ds.sqlite_functions.append(
             ('sleep', 1, lambda n: time.sleep(float(n))),
         )
-        client = TestClient(ds.app().test_client)
+        m = re.search(r'[0-9]+', worker_id)
+        if m:
+            num_id = m.group(0)
+        else:
+            num_id = 0
+        port = PORT_BASE + int(num_id)
+        client = MyTestClient(SanicTestClient(ds.app(), port))
         client.ds = ds
         yield client
 
 
 @pytest.fixture(scope='session')
-def app_client_shorter_time_limit():
-    yield from app_client(20)
+def app_client_factory(worker_id):
+    def factory(**kwargs):
+        yield from app_client(worker_id, **kwargs)
+    return factory
 
 
 @pytest.fixture(scope='session')
-def app_client_returned_rows_matches_page_size():
-    yield from app_client(max_returned_rows=50)
+def app_client_shorter_time_limit(worker_id):
+    yield from app_client(worker_id, 20)
 
 
 @pytest.fixture(scope='session')
-def app_client_larger_cache_size():
-    yield from app_client(config={
+def app_client_returned_rows_matches_page_size(worker_id):
+    yield from app_client(worker_id, max_returned_rows=50)
+
+
+@pytest.fixture(scope='session')
+def app_client_larger_cache_size(worker_id):
+    yield from app_client(worker_id, config={
         'cache_size_kb': 2500,
     })
 
 
 @pytest.fixture(scope='session')
-def app_client_csv_max_mb_one():
-    yield from app_client(config={
+def app_client_csv_max_mb_one(worker_id):
+    yield from app_client(worker_id, config={
         'max_csv_mb': 1,
     })
 
 
 @pytest.fixture(scope="session")
-def app_client_with_dot():
-    yield from app_client(filename="fixtures.dot.db")
+def app_client_with_dot(worker_id):
+    yield from app_client(worker_id, filename="fixtures.dot.db")
 
 
 def generate_compound_rows(num):
diff --git a/tests/test_api.py b/tests/test_api.py
index 61987f0a..418494a0 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -1,5 +1,6 @@
 from .fixtures import ( # noqa
     app_client,
+    app_client_factory,
     app_client_shorter_time_limit,
     app_client_larger_cache_size,
     app_client_returned_rows_matches_page_size,
@@ -424,8 +425,8 @@ def test_invalid_custom_sql(app_client):
     assert 'Statement must be a SELECT' == response.json['error']
 
 
-def test_allow_sql_off():
-    for client in app_client(config={
+def test_allow_sql_off(worker_id):
+    for client in app_client(worker_id, config={
         'allow_sql': False,
     }):
         assert 400 == client.get(
@@ -971,11 +972,12 @@ def test_config_json(app_client):
     } == response.json
 
 
-def test_page_size_matching_max_returned_rows(app_client_returned_rows_matches_page_size):
+def test_page_size_matching_max_returned_rows(app_client_factory):
+    app_client = app_client_factory(max_returned_rows=50)
     fetched = []
     path = '/fixtures/no_primary_key.json'
     while path:
-        response = app_client_returned_rows_matches_page_size.get(path)
+        response = app_client.get(path)
         fetched.extend(response.json['rows'])
         assert len(response.json['rows']) in (1, 50)
         path = response.json['next_url']
@@ -1140,8 +1142,8 @@ def test_suggested_facets(app_client):
     ).json["suggested_facets"]) > 0
 
 
-def test_allow_facet_off():
-    for client in app_client(config={
+def test_allow_facet_off(worker_id):
+    for client in app_client(worker_id, config={
         'allow_facet': False,
     }):
         assert 400 == client.get(
@@ -1153,8 +1155,8 @@ def test_allow_facet_off():
         ).json["suggested_facets"]
 
 
-def test_suggest_facets_off():
-    for client in app_client(config={
+def test_suggest_facets_off(worker_id):
+    for client in app_client(worker_id, config={
         'suggest_facets': False,
     }):
         # Now suggested_facets should be []
diff --git a/tests/test_csv.py b/tests/test_csv.py
index 194de5b1..794cd9b3 100644
--- a/tests/test_csv.py
+++ b/tests/test_csv.py
@@ -30,6 +30,7 @@ pk,planet_int,on_earth,state,city_id,city_id_label,neighborhood
 15,2,0,MC,4,Memnonia,Arcadia Planitia
 '''.lstrip().replace('\n', '\r\n')
 
+
 def test_table_csv(app_client):
     response = app_client.get('/fixtures/simple_primary_key.csv')
     assert response.status == 200
diff --git a/tests/test_html.py b/tests/test_html.py
index ee9d3c41..a7c58442 100644
--- a/tests/test_html.py
+++ b/tests/test_html.py
@@ -639,8 +639,8 @@ def test_allow_download_on(app_client):
     assert len(soup.findAll('a', {'href': re.compile('\.db$')}))
 
 
-def test_allow_download_off():
-    for client in app_client(config={
+def test_allow_download_off(worker_id):
+    for client in app_client(worker_id, config={
         'allow_download': False,
     }):
         response = client.get(
@@ -665,8 +665,8 @@ def test_allow_sql_on(app_client):
     assert len(soup.findAll('textarea', {'name': 'sql'}))
 
 
-def test_allow_sql_off():
-    for client in app_client(config={
+def test_allow_sql_off(worker_id):
+    for client in app_client(worker_id, config={
         'allow_sql': False,
     }):
         response = client.get(