Use download cache in unit tests

During unit tests, replace ModController.extract_archive with a version
that caches extracted archives in /tmp, then copies them into ammo's mod
storage directory when extraction is requested.

This ensures that each archive must only be extracted once per test
session.

This also allows removing a condition from ModController.extract_archive
which previously prevented archive validation from taking place when the
unit tests were running.

This doubles execution speed of the test suite on my system.

Author: cyberrumor

ammo/controller/mod.py

@@ -406,15 +406,13 @@ def extract_archive(self, index: int, download: Path) -> Path:
             download.location = new_location
             download.name = new_location.name
 
-        if "pytest" not in sys.modules:
-            # Don't run this during tests because it's slow.
-            try:
-                print("Verifying archive integrity...")
-                subprocess.check_output(["7z", "t", f"{download.location}"])
-            except subprocess.CalledProcessError:
-                raise Warning(
-                    f"Extraction of {index} failed at integrity check. Incomplete download?"
-                )
+        try:
+            print("Verifying archive integrity...")
+            subprocess.check_output(["7z", "t", f"{download.location}"])
+        except subprocess.CalledProcessError:
+            raise Warning(
+                f"Extraction of {index} failed at integrity check. Incomplete download?"
+            )
 
         os.system(f"7z x '{download.location}' -o'{extract_to}'")
 

test/conftest.py

@@ -1,10 +1,52 @@
 #!/usr/bin/env python3
+import os
+import shutil
+from pathlib import Path
 from unittest.mock import patch
 
 import pytest
 
 from ammo.controller.mod import ModController
 
+EXTRACT_CACHE = Path("/tmp/ammo_extract_cache/")
+
+
+def get_cached_archive(self, index: int, download: Path) -> Path:
+    """
+    See if an extracted archive is cached. If it is, copy it to
+    /tmp/ammo_test/MockGame/mods/. If it's not, extract it, cache it,
+    then copy it to /tmp/ammo_test/MockGame/mods/.
+
+    Return Path("/tmp/ammo_test/MockGame/mods/<extracted_archive>")
+    """
+    extract_to_name = "".join(
+        [i for i in download.location.stem.replace(" ", "_") if i.isalnum() or i == "_"]
+    ).strip()
+
+    extract_to = self.game.ammo_mods_dir / extract_to_name
+    if extract_to.exists():
+        raise Warning(
+            f"Extraction of {index} failed since mod '{extract_to.name}' exists."
+        )
+
+    archive_at = EXTRACT_CACHE / extract_to_name
+    if not archive_at.exists():
+        os.system(f"7z x '{download.location}' -o'{archive_at}'")
+
+    os.system(f"cp -r {archive_at} {extract_to}")
+
+    return extract_to
+
+
+@pytest.fixture(scope="session", autouse=True)
+def mock_extract_archive():
+    try:
+        EXTRACT_CACHE.mkdir(parents=True, exist_ok=True)
+        with patch.object(ModController, "extract_archive", get_cached_archive):
+            yield
+    finally:
+        shutil.rmtree(EXTRACT_CACHE, ignore_errors=True)
+
 
 @pytest.fixture
 def mock_has_extra_folder():