refactor tests

* factor out duplicated code
* make tests an importable package
* idiomatic pytest usage
* do not touch files outside of the tmp test tree and do not depend on
  external state (except for /nix/store ☹)
* run coverage to root out dead code

tests/test_use_nix.py

@@ -1,67 +1,35 @@
+from __future__ import annotations
+
 import os
-import subprocess
-import sys
-import unittest
-from typing import Optional
 
 import pytest
-from direnv_project import DirenvProject
-from procs import run
+
+from .case import TestCase
 
 
-def direnv_exec(
-    direnv_project: DirenvProject, cmd: str, env: Optional[dict[str, str]] = None
-) -> None:
-    args = ["direnv", "exec", str(direnv_project.dir), "sh", "-c", cmd]
-    print("$ " + " ".join(args))
-    out = run(
-        args,
-        stderr=subprocess.PIPE,
-        stdout=subprocess.PIPE,
-        check=False,
-        cwd=direnv_project.dir,
-        env=env,
-    )
-    sys.stdout.write(out.stdout)
-    sys.stderr.write(out.stderr)
-    assert out.returncode == 0
-    assert "OK\n" == out.stdout
-    assert "renewed cache" in out.stderr
+class TestUseNix(TestCase):
+    @pytest.mark.parametrize("strict_env", [False, True])
+    def test_attrs(self, strict_env: bool) -> None:
+        self.setup_envrc("use nix -A subshell", strict_env=strict_env)
+        self.assert_direnv_var("THIS_IS_A_SUBSHELL")
 
+    @pytest.mark.parametrize("strict_env", [False, True])
+    def test_with_nix_path(self, strict_env: bool) -> None:
+        if (nix_path := os.environ.get("NIX_PATH")) is None:
+            pytest.skip("no parent NIX_PATH")
+        else:
+            self.setup_envrc(
+                "use nix --argstr someArg OK", strict_env=strict_env, NIX_PATH=nix_path
+            )
+            self.assert_direnv_var("SHOULD_BE_SET", NIX_PATH=nix_path)
 
-@pytest.mark.parametrize("strict_env", [False, True])
-def test_attrs(direnv_project: DirenvProject, strict_env: bool) -> None:
-    direnv_project.setup_envrc("use nix -A subshell", strict_env=strict_env)
-    direnv_exec(direnv_project, "echo $THIS_IS_A_SUBSHELL")
+    @pytest.mark.parametrize("strict_env", [False, True])
+    def test_args(self, strict_env: bool) -> None:
+        self.setup_envrc("use nix --argstr someArg OK", strict_env=strict_env)
+        self.assert_direnv_var("SHOULD_BE_SET")
 
-
-@pytest.mark.parametrize("strict_env", [False, True])
-def test_no_nix_path(direnv_project: DirenvProject, strict_env: bool) -> None:
-    direnv_project.setup_envrc("use nix --argstr someArg OK", strict_env=strict_env)
-    env = os.environ.copy()
-    del env["NIX_PATH"]
-    direnv_exec(direnv_project, "echo $SHOULD_BE_SET", env=env)
-
-
-@pytest.mark.parametrize("strict_env", [False, True])
-def test_args(direnv_project: DirenvProject, strict_env: bool) -> None:
-    direnv_project.setup_envrc("use nix --argstr someArg OK", strict_env=strict_env)
-    direnv_exec(direnv_project, "echo $SHOULD_BE_SET")
-
-
-@pytest.mark.parametrize("strict_env", [False, True])
-def test_no_files(direnv_project: DirenvProject, strict_env: bool) -> None:
-    direnv_project.setup_envrc("use nix -p hello", strict_env=strict_env)
-    out = run(
-        ["direnv", "status"],
-        stderr=subprocess.PIPE,
-        stdout=subprocess.PIPE,
-        check=False,
-        cwd=direnv_project.dir,
-    )
-    assert out.returncode == 0
-    assert 'Loaded watch: "."' not in out.stdout
-
-
-if __name__ == "__main__":
-    unittest.main()
+    @pytest.mark.parametrize("strict_env", [False, True])
+    def test_no_files(self, strict_env: bool) -> None:
+        self.setup_envrc("use nix -p hello", strict_env=strict_env)
+        result = self.direnv_run("status")
+        assert 'Loaded watch: "."' not in result.stdout