diff --git a/src/pkgcore/repository/util.py b/src/pkgcore/repository/util.py
index 7a0157d9f..2f9be4b4f 100644
--- a/src/pkgcore/repository/util.py
+++ b/src/pkgcore/repository/util.py
@@ -14,6 +14,67 @@
 from ..ebuild.cpv import VersionedCPV
 
 
+class SimpleTreeFromPkgs(prototype.tree):
+    """Repository adapter that can work from a sequence of instantiated packages
+
+    This is useful for generating a repository on the fly (package.provided) or for
+    test usage.
+    """
+
+    def __init__(
+        self,
+        packages: typing.Iterable,
+        livefs=False,
+        frozen=True,
+        repo_id: typing.Union[str, None] = None,
+    ):
+        """
+        Args:
+            packages: sequence of instantiated packages to use.  cpv.VersionedCPV for example,
+                or FakePkg.
+        """
+        super().__init__(frozen=frozen)
+        # just return the pkg we already have.
+        self.package_class = lambda x: x
+        self.repo_id = repo_id
+        self.livefs = livefs
+        self._packages = {}  # type: dict[str, dict[str, list[typing.Any]]]
+        for pkg in packages:
+            self.notify_add_package(pkg)
+
+    def _get_categories(self, *arg: tuple[str, ...]):
+        if arg:
+            return ()
+        return tuple(self._packages)
+
+    def _get_packages(self, category: str) -> typing.Iterable[str]:
+        return tuple(self._packages[category])
+
+    def _get_versions(self, cp_key: tuple[str, str]) -> typing.Iterable[str]:
+        return tuple(pkg.fullver for pkg in self._packages[cp_key[0]][cp_key[1]])
+
+    def notify_add_package(self, pkg):
+        self._packages.setdefault(pkg.category, {}).setdefault(pkg.package, []).append(
+            pkg
+        )
+        super().notify_add_package(pkg)
+
+    def notify_remove_package(self, pkg):
+        try:
+            pkgs = [
+                p
+                for p in self._packages[pkg.category][pkg.package]
+                if p.fullver != pkg.fullver
+            ]
+            if not pkgs:
+                del self._packages[pkg.category][pkg.package]
+                if not self._packages[pkg.category]:
+                    del self._packages[pkg.category]
+        except KeyError:
+            pass
+        super().notify_remove_package(pkg)
+
+
 class SimpleTree(prototype.tree):
     """in-memory repository used for testing or simple shims."""