$this->drupalPostForm('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add', $edit, t('Save'));
$this->drupalPostForm(NULL, ['field_test[0][alt]' => $this->randomMachineName()], t('Save'));
$terms = entity_load_multiple_by_properties('taxonomy_term', ['name' => $edit['name[0][value]']]);
$this->drupalPostForm('admin/structure/taxonomy/manage/' . $this->vocabulary->id() . '/add', $edit, t('Save'));
$this->drupalPostForm(NULL, ['field_test[0][alt]' => $this->randomMachineName()], t('Save'));
$terms = entity_load_multiple_by_properties('taxonomy_term', ['name' => $edit['name[0][value]']]);