Add tests

modin/backends/pandas/query_compiler.py

@@ -495,7 +495,7 @@ def to_pandas(self):
                     self.dtypes
                 )
             else:
-                df = pandas.DataFrame(index=self.index)
+                df = pandas.DataFrame(columns=self.columns, index=self.index)
         else:
             ErrorMessage.catch_bugs_and_request_email(
                 len(df.index) != len(self.index) or len(df.columns) != len(self.columns)
@@ -1848,22 +1848,23 @@ def tail(self, n):
         # See head for an explanation of the transposed behavior
         if n < 0:
             n = max(0, len(self.index) + n)
-        if n == 0:
-            index = pandas.Index([])
-        else:
-            index = self.index[-n:]
         if self._is_transposed:
             result = self.__constructor__(
                 self.data.transpose().take(1, -n).transpose(),
-                index,
+                index[:-n],
                 self.columns,
                 self._dtype_cache,
             )
             result._is_transposed = True
         else:
-            result = self.__constructor__(
-                self.data.take(0, -n), index, self.columns, self._dtype_cache
-            )
+            if n == 0:
+                result = self.__constructor__(
+                    self.data.take(0, 0), self.index[:0], self.columns, self._dtype_cache
+                )
+            else:
+                result = self.__constructor__(
+                    self.data.take(0, -n), self.index[-n:], self.columns, self._dtype_cache
+                )
 
         return result
 

modin/pandas/base.py

@@ -2915,6 +2915,7 @@ def to_numpy(self, dtype=None, copy=False):
         """
         return self._default_to_pandas("to_numpy", dtype=dtype, copy=copy)
 
+    # TODO(williamma12): When this gets implemented, have the series one call this.
     def to_period(self, freq=None, axis=0, copy=True):  # pragma: no cover
         return self._default_to_pandas("to_period", freq=freq, axis=axis, copy=copy)
 
@@ -3003,6 +3004,7 @@ def to_sql(
             method=method,
         )
 
+    # TODO(williamma12): When this gets implemented, have the series one call this.
     def to_timestamp(self, freq=None, how="start", axis=0, copy=True):
         return self._default_to_pandas(
             "to_timestamp", freq=freq, how=how, axis=axis, copy=copy

modin/pandas/dataframe.py

@@ -1620,6 +1620,9 @@ def to_parquet(
             **kwargs
         )
 
+    def to_period(self, freq=None, axis=0, copy=True):  # pragma: no cover
+        return super(DataFrame, self).to_period(freq=freq, axis=axis, copy=copy)
+
     def to_records(
         self, index=True, convert_datetime64=None, column_dtypes=None, index_dtypes=None
     ):
@@ -1658,6 +1661,9 @@ def to_stata(
             convert_strl=convert_strl,
         )
 
+    def to_timestamp(self, freq=None, how="start", axis=0, copy=True):
+        return super(DataFrame, self).to_timestamp(freq=freq, how=how, axis=axis, copy=copy)
+
     def truediv(self, other, axis="columns", level=None, fill_value=None):
         if isinstance(other, Series):
             other = other._to_pandas()

modin/pandas/series.py

@@ -955,6 +955,13 @@ def to_list(self):
 
     tolist = to_list
 
+    # TODO(williamma12): When we implement to_timestamp, have this call the version
+    # in base.py
+    def to_period(self, freq=None, copy=True):
+        return self._default_to_pandas(
+            "to_period", freq=freq, copy=copy
+        )
+
     def to_string(
         self,
         buf=None,
@@ -980,6 +987,13 @@ def to_string(
             max_rows=max_rows,
         )
 
+    # TODO(williamma12): When we implement to_timestamp, have this call the version
+    # in base.py
+    def to_timestamp(self, freq=None, how="start", copy=True):
+        return self._default_to_pandas(
+            "to_timestamp", freq=freq, how=how, copy=copy
+        )
+
     def transpose(self, *args, **kwargs):
         return self