Bug fix #3593 - approx method in a single element of numpy array

If the user pass as a expected value a numpy array created like
numpy.array(5); it will creates an array with one element without shape,
when used with approx it will raise an error
'TypeError: iteration over a 0-d array'

testing/python/approx.py

@@ -27,8 +27,11 @@ class MyDocTestRunner(doctest.DocTestRunner):
 
 class TestApprox(object):
 
-    def test_repr_string(self):
-        plus_minus = u"\u00b1" if sys.version_info[0] > 2 else u"+-"
+    @pytest.fixture
+    def plus_minus(self):
+        return u"\u00b1" if sys.version_info[0] > 2 else u"+-"
+
+    def test_repr_string(self, plus_minus):
         tol1, tol2, infr = "1.0e-06", "2.0e-06", "inf"
         assert repr(approx(1.0)) == "1.0 {pm} {tol1}".format(pm=plus_minus, tol1=tol1)
         assert (
@@ -61,6 +64,18 @@ class TestApprox(object):
             ),
         )
 
+    def test_repr_0d_array(self, plus_minus):
+        np = pytest.importorskip("numpy")
+        np_array = np.array(5.)
+        assert approx(np_array) == 5.0
+        string_expected = "approx([5.0 {} 5.0e-06])".format(plus_minus)
+
+        assert repr(approx(np_array)) == string_expected
+
+        np_array = np.array([5.])
+        assert approx(np_array) == 5.0
+        assert repr(approx(np_array)) == string_expected
+
     def test_operator_overloading(self):
         assert 1 == approx(1, rel=1e-6, abs=1e-12)
         assert not (1 != approx(1, rel=1e-6, abs=1e-12))