diff --git a/tests/unit/cli/test_summary.py b/tests/unit/cli/test_summary.py
new file mode 100644
index 0000000..d2baae7
--- /dev/null
+++ b/tests/unit/cli/test_summary.py
@@ -0,0 +1,95 @@
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+
+<<<<<<< HEAD
+from stargraph.cli._summary import (
+    _fmt_duration,
+    _is_artifact_field,
+    _is_default,
+)  # pyright: ignore[reportPrivateUsage]
+
+=======
+from stargraph.cli._summary import (  # pyright: ignore[reportPrivateUsage]
+    _fmt_duration,
+    _is_artifact_field,
+    _is_default,
+)  
+>>>>>>> 834217e (et-ExecutionPolicy -Scope Process -ExecutionPolicy RemoteSigned) ; (&)
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    ("milliseconds", "expected"),
+    [
+        (500, "500ms"),
+        (1000, "1.0s"),
+        (1500, "1.5s"),
+    ],
+)
+def test_fmt_duration(milliseconds: int, expected: str) -> None:
+    assert _fmt_duration(milliseconds) == expected
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    "value",
+    [
+        None,
+        "",
+        [],
+        {},
+        0,
+        False,
+    ],
+)
+<<<<<<< HEAD
+def test_is_default_returns_true(value) -> None:
+=======
+def test_is_default_returns_true(value: object) -> None:
+>>>>>>> 834217e (et-ExecutionPolicy -Scope Process -ExecutionPolicy RemoteSigned) ; (&)
+    assert _is_default(value) is True
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    "value",
+    [
+        "x",
+        5,
+        [1],
+    ],
+)
+<<<<<<< HEAD
+def test_is_default_returns_false(value) -> None:
+=======
+def test_is_default_returns_false(value: object) -> None:
+>>>>>>> 834217e (et-ExecutionPolicy -Scope Process -ExecutionPolicy RemoteSigned) ; (&)
+    assert _is_default(value) is False
+
+
+@pytest.mark.unit
+def test_is_artifact_field_true() -> None:
+    assert (
+        _is_artifact_field(
+            "out_files",
+            {"a.txt": "hello"},
+        )
+        is True
+    )
+
+
+@pytest.mark.unit
+@pytest.mark.parametrize(
+    ("name", "value"),
+    [
+        ("output", {"a.txt": "hello"}),
+        ("out_files", []),
+        ("out_files", {"a.txt": 5}),
+    ],
+)
+<<<<<<< HEAD
+def test_is_artifact_field_false(name, value) -> None:
+=======
+def test_is_artifact_field_false(name: str, value: object) -> None:
+>>>>>>> 834217e (et-ExecutionPolicy -Scope Process -ExecutionPolicy RemoteSigned) ; (&)
+    assert _is_artifact_field(name, value) is False