Refactor tests' hard-coded *nix-style paths

Signed-off-by: Jack Leightcap <jack.leightcap@trailofbits.com>

test/test_cache.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+import os
 
 import pretend  # type: ignore
 from packaging.version import Version
@@ -9,15 +10,16 @@
 
 def test_get_cache_dir(monkeypatch):
     # When we supply a cache directory, always use that
-    cache_dir = _get_cache_dir(Path("/tmp/foo/cache_dir"))
-    assert str(cache_dir) == "/tmp/foo/cache_dir"
+    cache_dir = _get_cache_dir(os.path.join("tmp", "foo", "cache_dir"))
+    assert str(cache_dir) == os.path.join("tmp", "foo", "cache_dir")
 
-    get_pip_cache = pretend.call_recorder(lambda: "/fake/pip/cache/dir")
+    get_pip_cache = pretend.call_recorder(
+        lambda: os.path.join("fake", "pip", "cache", "dir"))
     monkeypatch.setattr(cache, "_get_pip_cache", get_pip_cache)
 
     # When `pip cache dir` works, we use it. In this case, it's mocked.
     cache_dir = _get_cache_dir(None, use_pip=True)
-    assert str(cache_dir) == "/fake/pip/cache/dir"
+    assert str(cache_dir) == os.path.join("fake", "pip", "cache", "dir")
 
 
 def test_get_pip_cache():
@@ -36,16 +38,17 @@ def test_get_cache_dir_pip_disabled_in_environment(monkeypatch):
     monkeypatch.setenv("PIP_NO_CACHE_DIR", "1")
 
     # Even with use_pip=True, we avoid pip's cache if the environment tells us to.
-    assert _get_cache_dir(None, use_pip=True) == Path.home() / ".pip-audit-cache"
+    assert _get_cache_dir(
+        None, use_pip=True) == Path.home() / ".pip-audit-cache"
 
 
 def test_get_cache_dir_old_pip(monkeypatch):
     # Check the case where we have an old `pip`
     monkeypatch.setattr(cache, "_PIP_VERSION", Version("1.0.0"))
 
     # When we supply a cache directory, always use that
-    cache_dir = _get_cache_dir(Path("/tmp/foo/cache_dir"))
-    assert str(cache_dir) == "/tmp/foo/cache_dir"
+    cache_dir = _get_cache_dir(os.path.join("tmp", "foo", "cache_dir"))
+    assert str(cache_dir) == os.path.join("tmp", "foo", "cache_dir")
 
     # In this case, we can't query `pip` to figure out where its HTTP cache is
     # Instead, we use `~/.pip-audit-cache`