Pass index maintenance test

Annoyingly I had to make our test csv all floats as I couldn't work out
how to get the dataframe testing to work without this

3 files changed, 44 insertions, 14 deletions

diff --git a/pint/pandas_interface/pint_array.py b/pint/pandas_interface/pint_array.py
index 42ebe65..c75c81b 100644
--- a/pint/pandas_interface/pint_array.py
+++ b/pint/pandas_interface/pint_array.py
@@ -500,21 +500,34 @@ class PintDataFrameAccessor(object):
         unit_col_name = df_columns.columns[level]
         units = df_columns[unit_col_name]
         df_columns = df_columns.drop(columns=unit_col_name)
-        df_columns.values
-        df_new = DataFrame({i: PintArray(Q_(df.values[:, i], unit))
+
+        df_new = DataFrame({
+            i: PintArray(Q_(df.values[:, i], unit))
             for i, unit in enumerate(units.values)
         })
+
         df_new.columns = df_columns.index.droplevel(unit_col_name)
         df_new.index = df.index
+
         return df_new
 
     def dequantify(self):
-        df=self._obj
-        df_columns=df.columns.to_frame()
-        df_columns['units']=[str(df[col].values.data.units) for col in df.columns]
-        df_new=DataFrame({ tuple(df_columns.iloc[i]) : df[col].values.data.magnitude
-            for i,col in enumerate(df.columns)
+        df = self._obj
+
+        df_columns = df.columns.to_frame()
+        df_columns['units'] = [
+            str(df[col].values.data.units)
+            for col in df.columns
+        ]
+
+        df_new = DataFrame({
+            tuple(df_columns.iloc[i]): df[col].values.data.magnitude
+            for i, col in enumerate(df.columns)
         })
+
+        df_new.columns.names = df.columns.names + ['unit']
+        df_new.index = df.index
+
         return df_new
 
     def to_base_units(self):
diff --git a/pint/testsuite/test-data/pandas_test.csv b/pint/testsuite/test-data/pandas_test.csv
index 93d912c..5301e81 100644
--- a/pint/testsuite/test-data/pandas_test.csv
+++ b/pint/testsuite/test-data/pandas_test.csv
@@ -1,6 +1,6 @@
 speed,mech power,torque,rail pressure,fuel flow rate,fluid power
 rpm,kW,N m,bar,l/min,kW
-1000,,10,1000,10,
-1100,,10,1000000000000,10,
-1200,,10,1000,10,
-1200,,10,1000,10,
+1000.0,,10.0,1000.0,10.0,
+1100.0,,10.0,1000000000000.0,10.0,
+1200.0,,10.0,1000.0,10.0,
+1200.0,,10.0,1000.0,10.0,
diff --git a/pint/testsuite/test_pandas_interface.py b/pint/testsuite/test_pandas_interface.py
index 5d607e4..0da478e 100644
--- a/pint/testsuite/test_pandas_interface.py
+++ b/pint/testsuite/test_pandas_interface.py
@@ -443,7 +443,6 @@ else:
                 "test-data", "pandas_test.csv"
             )
 
-
             df = pd.read_csv(test_csv, header=[0, 1])
             df.columns = pd.MultiIndex.from_arrays(
                 [
@@ -462,9 +461,27 @@ else:
 
             )
 
-            df_ = df.pint.quantify(ureg, level=-1).pint.dequantify()
 
-            pd.testing.assert_frame_equal(df, df_)
+            expected = df.copy()
+
+            # we expect the result to come back with pint names, not input
+            # names
+            def get_pint_value(in_str):
+                return str(ureg.Quantity(1, in_str).units)
+
+            units_level = [
+                i for i, name in enumerate(df.columns.names) if name == 'unit'
+            ][0]
+
+            expected.columns = df.columns.set_levels(
+                df.columns.levels[units_level].map(get_pint_value),
+                level='unit'
+            )
+
+
+            result = df.pint.quantify(ureg, level=-1).pint.dequantify()
+
+            pd.testing.assert_frame_equal(result, expected)
 
 
     class TestSeriesAccessors(object):