TST: error tests for diag_indices_from()

* add unit tests for previously uncovered
error handling code in diag_indices_from()

1 files changed, 17 insertions, 5 deletions

diff --git a/numpy/lib/tests/test_index_tricks.py b/numpy/lib/tests/test_index_tricks.py
index 33b98629d..aa3c7b8a4 100644
--- a/numpy/lib/tests/test_index_tricks.py
+++ b/numpy/lib/tests/test_index_tricks.py
@@ -365,11 +365,23 @@ def test_diag_indices():
         )
 
 
-def test_diag_indices_from():
-    x = np.random.random((4, 4))
-    r, c = diag_indices_from(x)
-    assert_array_equal(r, np.arange(4))
-    assert_array_equal(c, np.arange(4))
+class TestDiagIndicesFrom(object):
+
+    def test_diag_indices_from(self):
+        x = np.random.random((4, 4))
+        r, c = diag_indices_from(x)
+        assert_array_equal(r, np.arange(4))
+        assert_array_equal(c, np.arange(4))
+
+    def test_error_small_input(self):
+        x = np.ones(7)
+        with assert_raises_regex(ValueError, "at least 2-d"):
+            diag_indices_from(x)
+
+    def test_error_shape_mismatch(self):
+        x = np.zeros((3, 3, 2, 3), int)
+        with assert_raises_regex(ValueError, "equal length"):
+            diag_indices_from(x)
 
 
 def test_ndindex():