Added a check to make sure all elements of a sequence in pytest.approx are valid.

Author: Drew-Ack

_pytest/python_api.py

@@ -450,6 +450,9 @@ def approx(expected, rel=None, abs=None, nan_ok=False):
     elif isinstance(expected, Mapping):
         cls = ApproxMapping
     elif isinstance(expected, Sequence) and not isinstance(expected, String):
+        for value in expected:
+            if isinstance(value, (Sequence, String, Mapping)):
+                raise TypeError("Sequence contained a value that was not float or int")
         cls = ApproxSequence
     elif isinstance(expected, Decimal):
         cls = ApproxDecimal

changelog/3473.bugfix.rst

@@ -1 +1,2 @@
 ``pytest.approx`` does not handle strings, but this was not easily apparent so it now raises a ``TypeError`` when a string is passed in as the expected argument.
+``pytest.approx`` did not check all elements in a sequence to make sure they were valid type, a ``TypeError`` is now raised when an invalid element is in a sequence.