Add missing tests for parents dir creation

tests/test_backend_mixin.py

@@ -63,6 +63,15 @@ def test_open_write_new_file(self, faker):
 
         self.assert_text_equal(filename, content)
 
+    def test_open_write_new_file_with_prefix(self, faker):
+        filename = 'some/new/dir/test.text'
+        content = six.text_type(faker.sentence())
+
+        with self.backend.open(filename, 'w') as f:
+            f.write(content)
+
+        self.assert_text_equal(filename, content)
+
     def test_open_write_new_binary_file(self, faker):
         filename = 'test.bin'
         content = six.binary_type(faker.binary())
@@ -106,6 +115,12 @@ def test_write_file(self, faker, utils):
 
         self.assert_bin_equal('test.bin', content)
 
+    def test_write_with_prefix(self, faker):
+        content = six.text_type(faker.sentence())
+        self.backend.write('some/path/to/test.txt', content)
+
+        self.assert_text_equal('some/path/to/test.txt', content)
+
     def test_delete(self, faker):
         content = faker.sentence()
         self.put_file('file.test', content)