Add test to check numeric precision GH33234 (#51753)

Signed-off-by: Liang Yan <[email protected]>

Author: liang3zy22

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -1377,6 +1377,33 @@ def func(ser):
     tm.assert_frame_equal(res, expected)
 
 
+def test_groupby_agg_precision(any_real_numeric_dtype):
+    if any_real_numeric_dtype in tm.ALL_INT_NUMPY_DTYPES:
+        max_value = np.iinfo(any_real_numeric_dtype).max
+    if any_real_numeric_dtype in tm.FLOAT_NUMPY_DTYPES:
+        max_value = np.finfo(any_real_numeric_dtype).max
+    if any_real_numeric_dtype in tm.FLOAT_EA_DTYPES:
+        max_value = np.finfo(any_real_numeric_dtype.lower()).max
+    if any_real_numeric_dtype in tm.ALL_INT_EA_DTYPES:
+        max_value = np.iinfo(any_real_numeric_dtype.lower()).max
+
+    df = DataFrame(
+        {
+            "key1": ["a"],
+            "key2": ["b"],
+            "key3": pd.array([max_value], dtype=any_real_numeric_dtype),
+        }
+    )
+    arrays = [["a"], ["b"]]
+    index = MultiIndex.from_arrays(arrays, names=("key1", "key2"))
+
+    expected = DataFrame(
+        {"key3": pd.array([max_value], dtype=any_real_numeric_dtype)}, index=index
+    )
+    result = df.groupby(["key1", "key2"]).agg(lambda x: x)
+    tm.assert_frame_equal(result, expected)
+
+
 def test_groupby_aggregate_directory(reduction_func):
     # GH#32793
     if reduction_func in ["corrwith", "nth"]: