assertNodeViewText example

// Gather expected output values with the various formatters.     $formatter_plugin_manager = \Drupal::service('plugin.manager.field.formatter');
    $field_test_default_settings = $formatter_plugin_manager->getDefaultSettings('field_test_default');
    $field_test_with_prepare_view_settings = $formatter_plugin_manager->getDefaultSettings('field_test_with_prepare_view');
    $output = [
      'field_test_default' => $field_test_default_settings['test_formatter_setting'] . '|' . $value,
      'field_test_with_prepare_view' => $field_test_with_prepare_view_settings['test_formatter_setting_additional'] . '|' . $value . '|' . ($value + 1),
    ];

    // Check that the field is displayed with the default formatter in 'rss'     // mode (uses 'default'), and hidden in 'teaser' mode (uses custom settings).     $this->assertNodeViewText($node, 'rss', $output['field_test_default'], "The field is displayed as expected in view modes that use 'default' settings.");
    $this->assertNodeViewNoText($node, 'teaser', $value, "The field is hidden in view modes that use custom settings.");

    // Change formatter for 'default' mode, check that the field is displayed     // accordingly in 'rss' mode.     $edit = [
      'fields[field_test][type]' => 'field_test_with_prepare_view',
      'fields[field_test][region]' => 'content',
    ];
    $this->drupalGet('admin/structure/types/manage/' . $this->type . '/display');
    $this->submitForm($edit, 'Save');
    $this->assertNodeViewText($node, 'rss', $output['field_test_with_prepare_view'], "The field is displayed as expected in view modes that use 'default' settings.");