Testsuite - Add test case in test_116_9 about overcommit cpus-per-task

Verify srun -N1 -n2 -c1 -O completes on a one-CPU node instead of
remaining pending with Reason Resources. The case is added to the
canonical overcommit test (test_116_9) rather than a separate file, and
the redundant test_116_59 is removed.

Ticket: 25536

testsuite/python/tests/test_116_9.py

diff --git a/testsuite/python/tests/test_116_9.py b/testsuite/python/tests/test_116_9.py
index 4113604..61ca779 100644
--- a/testsuite/python/tests/test_116_9.py
+++ b/testsuite/python/tests/test_116_9.py
@@ -37,3 +37,32 @@
     assert (
         re.search(rf"srun: ntasks\s+: {cpu_count + 1}", results["stderr"]) is not None
     )
+
+
+@pytest.mark.skipif(
+    atf.get_version("sbin/slurmctld") < (26, 11),
+    reason="Ticket 25536: overcommit with cpus-per-task placement fix",
+)
+def test_overcommit_cpus_per_task():
+    """Verify srun -n2 -c1 --overcommit runs on a one-CPU node.
+
+    Ticket 25536: -cN sets tres_per_task=cpu=N; a cpu-only tres_per_task
+    must keep the overcommit placement path instead of leaving the job
+    pending with Reason Resources.
+    """
+    # Pin to a one-CPU node so -n2 cannot fit without overcommit.
+    eligible_node = None
+    for node in atf.nodes:
+        if "IDLE" in atf.nodes[node]["state"] and atf.nodes[node]["cpus"] == 1:
+            eligible_node = node
+            break
+    if eligible_node is None:
+        pytest.skip("This test requires one idle node with exactly 1 CPU")
+
+    results = atf.run_command(
+        f"srun -N1 -w {eligible_node} -n2 -c1 --overcommit -t1 -v /bin/true",
+        fatal=True,
+    )
+    assert (
+        re.search(r"srun: ntasks\s+: 2", results["stderr"]) is not None
+    ), "srun should launch 2 tasks on the one-CPU node with overcommit"