code: def test_v_stack_execution(setup):
      a_data = np.random.rand(10)
      b_data = np.random.rand(10)
  
      a = tensor(a_data, chunk_size=8)
      b = tensor(b_data, chunk_size=8)
  
      c = vstack([a, b])
      res = c.execute().fetch()
      expected = np.vstack([a_data, b_data])
      assert np.array_equal(res, expected) is True
  
      a_data = np.random.rand(10, 20)
      b_data = np.random.rand(5, 20)
  
      a = tensor(a_data, chunk_size=6)
      b = tensor(b_data, chunk_size=8)
  
      c = vstack([a, b])
      res = c.execute().fetch()
      expected = np.vstack([a_data, b_data])
      assert np.array_equal(res, expected) is True
  
file_path: mars/mars/tensor/merge/tests/test_merge_execution.py
imports: import numpy
  import scipy.sparse
  import pytest
  from ...datasource import tensor, empty, eye, ones, zeros
  from ...None import concatenate, stack, hstack, vstack, dstack, column_stack, union1d, array, block, append
label_desc: Use image node_id 4 for calling a global function with example usage: test_v_stack_execution(setup) without return types