tests/f2: make ManagedPath searchable

Change-Id: Idccf83a4471d76362153535125a269abbbb03c62

tests/functional2/testlib/fixtures/env.py

@@ -127,6 +127,12 @@ class _ManagedPath:
                 ret.append(p)
         return ret
 
+    def which(self, program_name: str) -> Path:
+        path = shutil.which(program_name, path=self.to_path())
+        if not path:
+            raise ValueError(f"{program_name} is not in configured path")
+        return Path(path)
+
 
 @dataclasses.dataclass
 class _Dirs:

tests/functional2/testlib/fixtures/test_env.py

@@ -223,3 +223,12 @@ def test_path_sandbox_entire_store_package():
     assert len(sb_paths) == 2
     assert sb_paths[0] == "/path/to/build_shell"
     assert re.fullmatch(r"^/nix/store/\w{32}-python3-3\.\d{1,2}\.\d{1,2}-[^/]+$", sb_paths[1])
+
+
+def test_path_which():
+    path = _ManagedPath("/path/to/build_shell")
+    with pytest.raises(ValueError, match="not in configured path"):
+        path.which("pytest")
+    wanted = shutil.which("pytest")
+    path.add_program(wanted)
+    assert str(path.which("pytest")) == wanted