test(spec): Control Server API secured via cross-pinning mTLS

. We are now leveraging nix for portable dependency handling.
. There are now three types of tests: client, server and end-to-end.
. server tests exercise the actual kapow server being tested, while the
requests are performed using the test steps.
. client tests exercise the actual kapow client being tested, while the
requests are served using the test steps.
. e2e test exercise the actual kapow program in its dual role of client
and server (¡como tiene que ser!).

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

spec/test/features/environment.py

@@ -15,25 +15,43 @@
 #
 import tempfile
 import os
+import signal
+from contextlib import suppress
 
-
-def before_scenario(context, scenario):
-    # Create the request_handler FIFO
+def tmpfifo():
     while True:
-        context.handler_fifo_path = tempfile.mktemp() # Safe because using
-                                                      # mkfifo
+        fifo_path = tempfile.mktemp() # The usage mkfifo make this safe
         try:
-            os.mkfifo(context.handler_fifo_path)
+            os.mkfifo(fifo_path)
         except OSError:
             # The file already exist
             pass
         else:
             break
 
+    return fifo_path
+
+
+def before_scenario(context, scenario):
+    context.handler_fifo_path = tmpfifo()
+    context.init_script_fifo_path = tmpfifo()
+
 
 def after_scenario(context, scenario):
+    # Real Kapow! server being tested
     if hasattr(context, 'server'):
         context.server.terminate()
         context.server.wait()
 
     os.unlink(context.handler_fifo_path)
+    os.unlink(context.init_script_fifo_path)
+
+    # Mock HTTP server for testing
+    if hasattr(context, 'httpserver'):
+        context.response_ready.set()
+        context.httpserver.shutdown()
+        context.httpserver_thread.join()
+
+    if getattr(context, 'testing_handler_pid', None) is not None:
+        with suppress(ProcessLookupError):
+            os.kill(int(context.testing_handler_pid), signal.SIGTERM)