Adds checks for nested data structures not of the same type as the outermost structure.

src/_pytest/python_api.py

@@ -376,7 +376,9 @@ class ApproxSequenceLike(ApproxBase):
     def _check_type(self) -> None:
         __tracebackhide__ = True
         for index, x in enumerate(self.expected):
-            if isinstance(x, type(self.expected)):
+            if (isinstance(x, Collection) or isinstance(x, Mapping)) and not isinstance(
+                x, STRING_TYPES
+            ):
                 msg = "pytest.approx() does not support nested data structures: {!r} at index {}\n  full sequence: {}"
                 raise TypeError(msg.format(x, index, pprint.pformat(self.expected)))
 

testing/python/approx.py

@@ -781,6 +781,9 @@ class TestApprox:
         "x, name",
         [
             pytest.param([[1]], "data structures", id="nested-list"),
+            pytest.param([(1,)], "data structures", id="nested-list-tuple"),
+            pytest.param([{1}], "data structures", id="nested-list-set"),
+            pytest.param([{"key": 1}], "data structures", id="nested-list-dict"),
             pytest.param({"key": {"key": 1}}, "dictionaries", id="nested-dict"),
         ],
     )