diff --git a/argopy/tests/helpers/mocked_http.py b/argopy/tests/helpers/mocked_http.py
index 01dbde35..d753fbf3 100644
--- a/argopy/tests/helpers/mocked_http.py
+++ b/argopy/tests/helpers/mocked_http.py
@@ -25,9 +25,7 @@
 
 """
 import contextlib
-import json
-import os
-import sys
+from pathlib import Path
 import threading
 from collections import ChainMap
 from http.server import BaseHTTPRequestHandler, HTTPServer
@@ -36,60 +34,86 @@
 from urllib.parse import unquote
 import socket
 import json
+import importlib
 
 
 log = logging.getLogger("argopy.tests.mocked_http")
-LOG_SERVER_CONTENT = False  # Also log the list of files/uris available from the mocked server
+LOG_SERVER_CONTENT = (
+    False  # Should we list files/uris available from the mocked server in the log ?
+)
 
 requests = pytest.importorskip("requests")
 port = 9898  # Select the port to run the local server on
 mocked_server_address = "http://127.0.0.1:%i" % port
 
-start_with = lambda f, x: f[0:len(x)] == x if len(x) <= len(f) else False  # noqa: E731
+start_with = (
+    lambda f, x: f[0 : len(x)] == x if len(x) <= len(f) else False
+)  # noqa: E731
 
-sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', '..'))
-from argopy.data_fetchers.erddap_data import api_server as erddap_api_server
+"""
+Load test data and create a dictionary mapping of URL requests as keys, and expected responses as values
 
-# Dictionary mapping of URL requests as keys, and expected responses as values:
-# (this will be filling the mocked http server content)
-# The real address must be made relative
+This will be filling the mocked http server content.
+The uri requested will be made relative, because the server name will be replaced by the mocked server address.
+"""
 MOCKED_REQUESTS = {}
-DATA_FOLDER = os.path.dirname(os.path.realpath(__file__)).replace("helpers", "test_data")
-DB_FILE = os.path.join(DATA_FOLDER, "httpmocked_uri_index.json")
-if os.path.exists(DB_FILE):
+TESTDATA_FOLDER = (
+    Path(importlib.util.find_spec("argopy.tests").submodule_search_locations[0])
+    .resolve()
+    .joinpath("test_data")
+)
+if not TESTDATA_FOLDER.exists():
+    raise RuntimeError(
+        "Can't find tests data folder at: %s\n Note that test data are not included in the pypi distribution. You should fork the repo to get test data."
+        % TESTDATA_FOLDER
+    )
+
+DB_FILE = TESTDATA_FOLDER.joinpath("httpmocked_uri_index.json")
+URI = []
+
+if DB_FILE.exists():
     with open(DB_FILE, "r") as f:
         URI = json.load(f)
     for resource in URI:
-        test_data_file = os.path.join(DATA_FOLDER, "%s.%s" % (resource['sha'], resource['ext']))
-        with open(test_data_file, mode='rb') as file:
+        test_data_file = TESTDATA_FOLDER.joinpath(
+            "%s.%s" % (resource["sha"], resource["ext"])
+        )
+        with open(test_data_file, mode="rb") as file:
             data = file.read()
 
-        # Remove all specific api/server, that will be served by the mocked http server:
+        # Remove all specific api/server names from absolute URIs
+        # Because these are arguments passed to methods that will use mocked_server_address instead
+        # (See for instance the argument 'server' in `argopy.data_fetchers.erddap_data.ErddapArgoDataFetcher`)
         patterns = [
-                "https://github.com/euroargodev/argopy-data/raw/master",
-                "https://erddap.ifremer.fr/erddap",
-                "https://data-argo.ifremer.fr",
-                "https://api.ifremer.fr",
-                "https://coastwatch.pfeg.noaa.gov/erddap",
-                "https://www.ocean-ops.org/api/1",
-                "https://dataselection.euro-argo.eu/api",
-                "https://vocab.nerc.ac.uk/collection",
-                "https://argovisbeta02.colorado.edu",
-                "https://dx.doi.org",
-                "https://archimer.ifremer.fr",
+            "https://github.com/euroargodev/argopy-data/raw/master",
+            "https://erddap.ifremer.fr/erddap",
+            "https://data-argo.ifremer.fr",
+            "https://api.ifremer.fr",
+            "https://coastwatch.pfeg.noaa.gov/erddap",
+            "https://www.ocean-ops.org/api/1",
+            "https://dataselection.euro-argo.eu/api",
+            "https://vocab.nerc.ac.uk/collection",
+            "https://argovisbeta02.colorado.edu",
+            "https://dx.doi.org",
+            "https://archimer.ifremer.fr",
         ]
         for pattern in patterns:
-            if start_with(resource['uri'], pattern):
-                MOCKED_REQUESTS[resource['uri'].replace(pattern, "")] = data
+            if start_with(resource["uri"], pattern):
+                MOCKED_REQUESTS[resource["uri"].replace(pattern, "")] = data
 
 else:
-    log.debug("Loading this sub-module without DB_FILE ! %s" % DB_FILE)
+    raise RuntimeError(
+        "Can't find test data index file at: %s.\n Note that test data are not included in the pypi distribution. You should fork the repo to get test data."
+        % DB_FILE
+    )
 
 
 def get_html_landing_page():
     """Return a webpage with a listing of all available files with a href links"""
     html = ["<html><head></head><body>\n"]
-    html.append("<h1>Mocked HTTP server is up and running, serving %i files</h1>" % len(URI))
+    html.append(
+        "<h1>Mocked HTTP server is up and running, serving %i files</h1>" % len(URI)
+    )
     html.append("<ul>")
     for key, value in MOCKED_REQUESTS.items():
         html.append("<li><a href='%s'>%s</a></li>" % (key, key))
@@ -101,10 +125,6 @@ def get_html_landing_page():
 class HTTPTestHandler(BaseHTTPRequestHandler):
     static_files = {
         "": get_html_landing_page(),
-        # "": b"Mocked HTTP server is up and running, serving %i files" % len(URI),  # This is mandatory for the server to respond without content
-        # "/index/otherfile": data,
-        # "/index": index,
-        # "/data/20020401": listing,
     }
     dynamic_files = {}
 
@@ -150,25 +170,26 @@ def do_GET(self):
         if file_data is None:
             # log.debug("file data empty, returning 404")
             return self._respond(404)
+        else:
+            n = len(file_data)
 
         status = 200
-        content_range = "bytes 0-%i/%i" % (len(file_data) - 1, len(file_data))
+        content_range = "bytes 0-%i/%i" % (n - 1, n)
         if ("Range" in self.headers) and ("ignore_range" not in self.headers):
             ran = self.headers["Range"]
             b, ran = ran.split("=")
             start, end = ran.split("-")
             if start:
-                content_range = f"bytes {start}-{end}/{len(file_data)}"
-                file_data = file_data[int(start): (int(end) + 1) if end else None]
+                content_range = f"bytes {start}-{end}/{n}"
+                file_data = file_data[int(start) : (int(end) + 1) if end else None]
             else:
                 # suffix only
-                l = len(file_data)
-                content_range = f"bytes {l - int(end)}-{l - 1}/{l}"
-                file_data = file_data[-int(end):]
+                content_range = f"bytes {n - int(end)}-{n - 1}/{n}"
+                file_data = file_data[-int(end) :]
             if "use_206" in self.headers:
                 status = 206
         if "give_length" in self.headers:
-            response_headers = {"Content-Length": len(file_data)}
+            response_headers = {"Content-Length": n}
             self._respond(status, response_headers, file_data)
         elif "give_range" in self.headers:
             self._respond(status, {"Content-Range": content_range}, file_data)
@@ -199,8 +220,8 @@ def read_chunks(self):
             self.rfile.readline()
 
     def do_HEAD(self):
-        self.headers.add_header('head_ok', '')
-        self.headers.add_header('give_length', '')
+        self.headers.add_header("head_ok", "")
+        self.headers.add_header("give_length", "")
 
         if "head_not_auth" in self.headers:
             return self._respond(
@@ -213,16 +234,18 @@ def do_HEAD(self):
         file_data = self.files.get(file_path)
         if file_data is None:
             return self._respond(404)
+        else:
+            n = len(file_data)
 
         if ("give_length" in self.headers) or ("head_give_length" in self.headers):
-            response_headers = {"Content-Length": len(file_data)}
+            response_headers = {"Content-Length": n}
             if "zero_length" in self.headers:
                 response_headers["Content-Length"] = 0
 
             self._respond(200, response_headers)
         elif "give_range" in self.headers:
             self._respond(
-                200, {"Content-Range": "0-%i/%i" % (len(file_data) - 1, len(file_data))}
+                200, {"Content-Range": "0-%i/%i" % (n - 1, n)}
             )
         elif "give_etag" in self.headers:
             self._respond(200, {"ETag": "xxx"})
@@ -238,8 +261,10 @@ def serve_mocked_httpserver():
     th.daemon = True
     th.start()
     try:
-        log.info("Mocked HTTP server up and ready at %s, serving %i URI. (id=%s)" %
-                 (mocked_server_address, len(HTTPTestHandler.files), id(httpd)))
+        log.info(
+            "Mocked HTTP server up and ready at %s, serving %i URI. (id=%s)"
+            % (mocked_server_address, len(HTTPTestHandler.files), id(httpd))
+        )
         if LOG_SERVER_CONTENT:
             # Use these lines to log test data name and content
             for f in HTTPTestHandler.files.keys():