ARROW-8398: [Python] Remove deprecated API usage from python tests

Closes #6897 from kszucs/python-warnings

Authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Signed-off-by: Wes McKinney <wesm+git@apache.org>

python/pyarrow/tests/test_array.py

@@ -54,7 +54,7 @@ def test_constructor_raises():
 
 def test_list_format():
     arr = pa.array([[1], None, [2, 3, None]])
-    result = arr.format()
+    result = arr.to_string()
     expected = """\
 [
   [
@@ -72,7 +72,7 @@ def test_list_format():
 
 def test_string_format():
     arr = pa.array(['', None, 'foo'])
-    result = arr.format()
+    result = arr.to_string()
     expected = """\
 [
   "",
@@ -84,7 +84,7 @@ def test_string_format():
 
 def test_long_array_format():
     arr = pa.array(range(100))
-    result = arr.format(window=2)
+    result = arr.to_string(window=2)
     expected = """\
 [
   0,
@@ -98,7 +98,7 @@ def test_long_array_format():
 
 def test_binary_format():
     arr = pa.array([b'\x00', b'', None, b'\x01foo', b'\x80\xff'])
-    result = arr.format()
+    result = arr.to_string()
     expected = """\
 [
   00,

python/pyarrow/tests/test_plasma.py

@@ -367,15 +367,15 @@ def test_store_arrow_objects(self):
         # Write an arrow object.
         object_id = random_object_id()
         tensor = pa.Tensor.from_numpy(data)
-        data_size = pa.get_tensor_size(tensor)
+        data_size = pa.ipc.get_tensor_size(tensor)
         buf = self.plasma_client.create(object_id, data_size)
         stream = pa.FixedSizeBufferWriter(buf)
-        pa.write_tensor(tensor, stream)
+        pa.ipc.write_tensor(tensor, stream)
         self.plasma_client.seal(object_id)
         # Read the arrow object.
         [tensor] = self.plasma_client.get_buffers([object_id])
         reader = pa.BufferReader(tensor)
-        array = pa.read_tensor(reader).to_numpy()
+        array = pa.ipc.read_tensor(reader).to_numpy()
         # Assert that they are equal.
         np.testing.assert_equal(data, array)
 
@@ -408,7 +408,7 @@ def test_store_pandas_dataframe(self):
         reader = pa.RecordBatchStreamReader(pa.BufferReader(data))
         result = reader.read_next_batch().to_pandas()
 
-        pd.util.testing.assert_frame_equal(df, result)
+        pd.testing.assert_frame_equal(df, result)
 
     def test_pickle_object_ids(self):
         # This can be used for sharing object IDs between processes.