'Check output for merging option \'Find matching rows\' by
Source position (index)'

def test_output_merge_by_ids_inner(self):

    domain = self.dataA.domain
    result = Table(domain, np.array([[1, 1], [2, 0]]), np.array([1, 2]), np.array([[1.0, 'm2'], [np.nan, 'm3']]).astype(object))
    self.send_signal(self.widget.Inputs.data, self.dataA[:3, [0, 'cls', (-1)]])
    self.send_signal(self.widget.Inputs.extra_data, self.dataA[1:, [1, 'cls', (-2)]])
    self.widget.attr_merge_data = 'Source    position    (index)'
    self.widget.attr_merge_extra = 'Source    position    (index)'
    self.widget.controls.merging.buttons[1].click()
    self.assertTablesEqual(self.get_output(self.widget.Outputs.data), result)
