TST: Bare pytest raises

pandas/tests/arrays/boolean/test_arithmetic.py

@@ -46,7 +46,7 @@ def test_add_mul(left_array, right_array, opname, exp):
 
 
 def test_sub(left_array, right_array):
-    with pytest.raises(TypeError):
+    with tm.external_error_raised(TypeError):
         # numpy points to ^ operator or logical_xor function instead
         left_array - right_array
 
@@ -92,13 +92,29 @@ def test_error_invalid_values(data, all_arithmetic_operators):
     ops = getattr(s, op)
 
     # invalid scalars
-    with pytest.raises(TypeError):
+    msg = (
+        "ufunc '\\w+' did not contain a loop with signature matching types|"
+        "ufunc '\\w+' not supported for the input types, and the inputs could "
+        "not be safely coerced to any supported types|"
+        "\\w+ cannot perform the operation \\w+"
+    )
+    with pytest.raises(TypeError, match=msg):
         ops("foo")
-    with pytest.raises(TypeError):
+
+    msg = (
+        "unsupported operand type\\(s\\) for|"
+        "Concatenation operation is not implemented for NumPy arrays"
+    )
+    with pytest.raises(TypeError, match=msg):
         ops(pd.Timestamp("20180101"))
 
     # invalid array-likes
     if op not in ("__mul__", "__rmul__"):
         # TODO(extension) numpy's mul with object array sees booleans as numbers
-        with pytest.raises(TypeError):
+        msg = (
+            "unsupported operand type\\(s\\) for|"
+            'can only concatenate str \\(not "bool"\\) to str|'
+            "not all arguments converted during string formatting"
+        )
+        with pytest.raises(TypeError, match=msg):
             ops(pd.Series("foo", index=s.index))

pandas/tests/extension/base/ops.py

@@ -30,7 +30,17 @@ def _check_op(self, s, op, other, op_name, exc=NotImplementedError):
                 expected = s.combine(other, op)
                 self.assert_series_equal(result, expected)
         else:
-            with pytest.raises(exc):
+            msg = (
+                "unsupported operand type\\(s\\) for|"
+                "cannot perform [\\w_]+ with this index type: [\\w_]+|"
+                "Object with dtype category cannot perform the numpy op [\\w_]+|"
+                "cannot add [\\w_]+ and [\\w_]+|"
+                "can't multiply sequence by non-int of type '[\\w_]+'|"
+                'can only concatenate str \\(not "[\\w_]+"\\) to str|'
+                "Object with dtype category cannot perform the numpy op [\\w_]+|"
+                "Concatenation operation is not implemented for NumPy arrays"
+            )
+            with pytest.raises(exc, match=msg):
                 op(s, other)
 
     def _check_divmod_op(self, s, op, other, exc=Exception):
@@ -44,7 +54,12 @@ def _check_divmod_op(self, s, op, other, exc=Exception):
             self.assert_series_equal(result_div, expected_div)
             self.assert_series_equal(result_mod, expected_mod)
         else:
-            with pytest.raises(exc):
+            msg = (
+                "'tuple' object has no attribute 'dtype'|"
+                "cannot perform __r?divmod__ with this index type|"
+                "unsupported operand type\\(s\\) for divmod\\(\\)"
+            )
+            with pytest.raises(exc, match=msg):
                 divmod(s, other)
 
 
@@ -111,7 +126,8 @@ def test_add_series_with_extension_array(self, data):
     def test_error(self, data, all_arithmetic_operators):
         # invalid ops
         op_name = all_arithmetic_operators
-        with pytest.raises(AttributeError):
+        msg = "'[\\w_]+' object has no attribute '[\\w_]+'"
+        with pytest.raises(AttributeError, match=msg):
             getattr(data, op_name)
 
     @pytest.mark.parametrize("box", [pd.Series, pd.DataFrame])
@@ -145,7 +161,8 @@ def _compare_other(self, s, data, op_name, other):
 
             # series
             s = pd.Series(data)
-            with pytest.raises(TypeError):
+            msg = "not supported between instances of '[\\w._]+' and '[\\w._]+'"
+            with pytest.raises(TypeError, match=msg):
                 op(s, other)
 
     def test_compare_scalar(self, data, all_compare_operators):

pandas/tests/extension/base/setitem.py

@@ -282,8 +282,25 @@ def test_setitem_loc_iloc_slice(self, data):
         self.assert_equal(result, expected)
 
     def test_setitem_slice_mismatch_length_raises(self, data):
+        # This class is a test mixin class, based on which test class it's mixed
+        # with the expected error messages can vary. This regular expression
+        # catches all the variants of those messages. It's formatted as a big OR
+        # statement: /m1|m2|m3|m4/
+
+        msg = (
+            # pandas.core.arrays.period.PeriodArray
+            # pandas.core.arrays.datetimes.DatetimeArray
+            "cannot set using a slice indexer with a different length than the value|"
+            # string_arrow.ArrowStringArray
+            "Length of indexer and values mismatch|"
+            # pandas.tests.extension.decimal.array.DecimalArray
+            "cannot copy sequence with size \\d to array axis with dimension \\d|"
+            # All the rest
+            "could not broadcast input array from "
+            "shape \\(\\d,?\\) into shape \\(\\d,?\\)"
+        )
         arr = data[:5]
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match=msg):
             arr[:1] = arr[:2]
 
     def test_setitem_slice_array(self, data):
@@ -292,8 +309,17 @@ def test_setitem_slice_array(self, data):
         self.assert_extension_array_equal(arr, data[-5:])
 
     def test_setitem_scalar_key_sequence_raise(self, data):
+        # Check the comment on test_setitem_slice_mismatch_length_raises for more info.
+        msg = (
+            # pandas.core.arrays.string_arrow.ArrowStringArray
+            "Must pass scalars with scalar indexer|"
+            # pandas.core.arrays.datetimes.DatetimeArray
+            "Could not convert object to NumPy datetime|"
+            # All the rest
+            "setting an array element with a sequence"
+        )
         arr = data[:5].copy()
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match=msg):
             arr[0] = arr[[0, 1]]
 
     def test_setitem_preserves_views(self, data):

pandas/tests/util/test_assert_series_equal.py

@@ -292,9 +292,22 @@ def test_series_equal_exact_for_nonnumeric():
     tm.assert_series_equal(s1, s2, check_exact=True)
     tm.assert_series_equal(s2, s1, check_exact=True)
 
-    with pytest.raises(AssertionError):
+    msg = """Series are different
+
+Series values are different \\(100\\.0 %\\)
+\\[index\\]: \\[0, 1\\]
+\\[left\\]:  \\[a, b\\]
+\\[right\\]: \\[b, a\\]"""
+    with pytest.raises(AssertionError, match=msg):
         tm.assert_series_equal(s1, s3, check_exact=True)
-    with pytest.raises(AssertionError):
+
+    msg = """Series are different
+
+Series values are different \\(100\\.0 %\\)
+\\[index\\]: \\[0, 1\\]
+\\[left\\]:  \\[b, a\\]
+\\[right\\]: \\[a, b\\]"""
+    with pytest.raises(AssertionError, match=msg):
         tm.assert_series_equal(s3, s1, check_exact=True)