[V3] Make pytest fixtures available as a plugin (#1858)

* Move all fixtures to pytest plugin folder

* Add core dunder all

* Update other dunder all's

* Black reformat

redbot/pytest/downloader.py

@@ -0,0 +1,103 @@
+from collections import namedtuple
+from pathlib import Path
+import json
+
+import pytest
+
+from redbot.cogs.downloader.repo_manager import RepoManager, Repo
+from redbot.cogs.downloader.installable import Installable
+
+__all__ = [
+    "patch_relative_to",
+    "repo_manager",
+    "repo",
+    "repo_norun",
+    "bot_repo",
+    "INFO_JSON",
+    "installable",
+    "fake_run_noprint",
+]
+
+
+async def fake_run(*args, **kwargs):
+    fake_result_tuple = namedtuple("fake_result", "returncode result")
+    res = fake_result_tuple(0, (args, kwargs))
+    print(args[0])
+    return res
+
+
+async def fake_run_noprint(*args, **kwargs):
+    fake_result_tuple = namedtuple("fake_result", "returncode result")
+    res = fake_result_tuple(0, (args, kwargs))
+    return res
+
+
+@pytest.fixture(scope="module", autouse=True)
+def patch_relative_to(monkeysession):
+    def fake_relative_to(self, some_path: Path):
+        return self
+
+    monkeysession.setattr("pathlib.Path.relative_to", fake_relative_to)
+
+
+@pytest.fixture
+def repo_manager(tmpdir_factory):
+    rm = RepoManager()
+    # rm.repos_folder = Path(str(tmpdir_factory.getbasetemp())) / 'repos'
+    return rm
+
+
+@pytest.fixture
+def repo(tmpdir):
+    repo_folder = Path(str(tmpdir)) / "repos" / "squid"
+    repo_folder.mkdir(parents=True, exist_ok=True)
+
+    return Repo(
+        url="https://github.com/tekulvw/Squid-Plugins",
+        name="squid",
+        branch="rewrite_cogs",
+        folder_path=repo_folder,
+    )
+
+
+@pytest.fixture
+def repo_norun(repo):
+    repo._run = fake_run
+    return repo
+
+
+@pytest.fixture
+def bot_repo(event_loop):
+    cwd = Path.cwd()
+    return Repo(
+        name="Red-DiscordBot",
+        branch="WRONG",
+        url="https://empty.com/something.git",
+        folder_path=cwd,
+        loop=event_loop,
+    )
+
+
+# Installable
+INFO_JSON = {
+    "author": ("tekulvw",),
+    "bot_version": (3, 0, 0),
+    "description": "A long description",
+    "hidden": False,
+    "install_msg": "A post-installation message",
+    "required_cogs": {},
+    "requirements": ("tabulate"),
+    "short": "A short description",
+    "tags": ("tag1", "tag2"),
+    "type": "COG",
+}
+
+
+@pytest.fixture
+def installable(tmpdir):
+    cog_path = tmpdir.mkdir("test_repo").mkdir("test_cog")
+    info_path = cog_path.join("info.json")
+    info_path.write_text(json.dumps(INFO_JSON), "utf-8")
+
+    cog_info = Installable(Path(str(cog_path)))
+    return cog_info