From c08bb9d93db82635bd63eb0a063d2042a53710cd Mon Sep 17 00:00:00 2001
From: Josh Bazar <45159255+TameTheGame@users.noreply.github.com>
Date: Tue, 8 Sep 2026 20:27:06 -0400
Subject: [PATCH] test(postprocessing): check signed magnitudes in 1-D faceflow
 cases

---
 autotest/test_postprocessing.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/autotest/test_postprocessing.py b/autotest/test_postprocessing.py
index fcebe5fbf..5aebc0f21 100644
--- a/autotest/test_postprocessing.py
+++ b/autotest/test_postprocessing.py
@@ -149,6 +149,16 @@ def test_get_structured_faceflows(function_tmpdir, nlay, nrow, ncol):
     assert np.any(fff) == (nrow > 1)
     assert np.any(flf) == (nlay > 1)
 
+    if nlay * nrow * ncol == 3:
+        # The 1-D cases have unit K and cell dimensions, with all heads
+        # prescribed as 11, 12, 13. Darcy flow is -1 toward increasing
+        # column, row, or layer number; the final face has no neighbor.
+        expected = np.array([-1.0, -1.0, 0.0]).reshape(nlay, nrow, ncol)
+        for flow, size in zip((frf, fff, flf), (ncol, nrow, nlay)):
+            if size == 3:
+                np.testing.assert_allclose(flow, expected, rtol=0.0, atol=1e-8)
+                assert flow.flat[-1] == 0.0
+
 
 @pytest.mark.mf6
 @requires_exe("mf6")