sdks/python: update delete test case for GCS

In this commit, we update the delete test to verify
recursive deletion of directories (prefixes) in GCS.

Changes include:
- Added test for deleting a GCS directory (prefix) with multiple files.
- Verified files under a directory are deleted recursively when using the delete method.

sdks/python/apache_beam/io/gcp/gcsio_test.py

@@ -153,6 +153,10 @@ def delete_blob(self, name, **kwargs):
     if name in bucket.blobs:
       del bucket.blobs[name]
 
+  def list_blobs(self, prefix=None, **kwargs):
+    bucket = self._get_canonical_bucket()
+    return self.client.list_blobs(bucket, prefix, **kwargs)
+
 
 class FakeBlob(object):
   def __init__(
@@ -445,20 +449,43 @@ def test_bad_file_modes(self):
       self.gcs.open(file_name, 'r+b')
 
   def test_delete(self):
+    # File path.
     file_name = 'gs://gcsio-test/delete_me'
     file_size = 1024
     bucket_name, blob_name = gcsio.parse_gcs_path(file_name)
+
     # Test deletion of non-existent file.
     bucket = self.client.get_bucket(bucket_name)
     self.gcs.delete(file_name)
 
+    # Insert a random file for testing.
     self._insert_random_file(self.client, file_name, file_size)
     self.assertTrue(blob_name in bucket.blobs)
 
+    # Deleting the file.
     self.gcs.delete(file_name)
-
     self.assertFalse(blob_name in bucket.blobs)
 
+    # Now test deleting a directory (prefix) with multiple files.
+    prefix = 'gs://gcsio-test/directory_to_delete/'
+    file_names = [f"{prefix}file1", f"{prefix}file2", f"{prefix}file3"]
+    blobs = [gcsio.parse_gcs_path(file_name) for file_name in file_names]
+
+    # Insert random files under the prefix.
+    for file_name in file_names:
+      self._insert_random_file(self.client, file_name, file_size)
+
+    # Verify the files exist before deletion
+    for blob in blobs:
+      self.assertTrue(blob[1] in bucket.blobs)
+
+    # Deleting the directory (all files under the prefix).
+    self.gcs.delete(prefix, recursive=True)
+
+    # Verify that the files are deleted.
+    for blob in blobs:
+      self.assertFalse(blob[1] in bucket.blobs)
+
   def test_copy(self):
     src_file_name = 'gs://gcsio-test/source'
     dest_file_name = 'gs://gcsio-test/dest'