TST: read_csv to nullable int dtype (pandas-dev#25472)

Author: alexreg

pandas/tests/io/parser/dtypes/test_nullable.py

@@ -0,0 +1,52 @@
+"""
+Tests dtype specification during parsing
+for all of the parsers defined in parsers.py
+"""
+from io import StringIO
+
+import pytest
+
+import pandas as pd
+from pandas import DataFrame
+import pandas._testing as tm
+from pandas.core.arrays.integer import (
+    Int8Dtype,
+    Int16Dtype,
+    Int32Dtype,
+    Int64Dtype,
+)
+
+
+@pytest.mark.parametrize(
+    "dtype",
+    [
+        "Int8",
+        "Int16",
+        "Int32",
+        "Int64",
+        Int8Dtype(),
+        Int16Dtype(),
+        Int32Dtype(),
+        Int64Dtype(),
+        {"a": "Int8", "b": "Int16", "c": Int32Dtype()},
+    ],
+)
+def test_integer_dtype(all_parsers, dtype):
+    # GH 25472
+    parser = all_parsers
+    data = """a,b,c
+,3,5
+1,,6
+2,4,"""
+    a_dtype = dtype["a"] if isinstance(dtype, dict) else dtype
+    b_dtype = dtype["b"] if isinstance(dtype, dict) else dtype
+    c_dtype = dtype["c"] if isinstance(dtype, dict) else dtype
+    expected = DataFrame(
+        {
+            "a": pd.array([pd.NA, 1, 2], dtype=a_dtype),
+            "b": pd.array([3, pd.NA, 4], dtype=b_dtype),
+            "c": pd.array([5, 6, pd.NA], dtype=c_dtype),
+        }
+    )
+    actual = parser.read_csv(StringIO(data), dtype=dtype)
+    tm.assert_frame_equal(actual, expected)