anchor.diff:  /// The tests themselves can then be provided via mixin, allowing summaries to
   /// be tested in a variety of ways.
   abstract class SummaryBaseTestStrategy {
  -  /**
  -   * Add the given source file so that it may be referenced by the file under
  -   * test.
  -   */
  +  /// Add the given source file so that it may be referenced by the file under
  +  /// test.
     void addNamedSource(String filePath, String contents);
   }
   
  
positive.code: /// The tests themselves can then be provided via mixin, allowing summaries to
  /// be tested in a variety of ways.
  abstract class SummaryBlackBoxTestStrategy extends SummaryBaseTestStrategy {
    /**
     * A test will set this to `true` if it contains `import`, `export`, or
     * `part` declarations that deliberately refer to non-existent files.
     */
    void set allowMissingFiles(bool value);
  
    /// Indicates whether the summary contains expressions for non-const fields.
  
negative.code:   return unit;
  }
  
  /// Verify invariants of the given [linkedLibrary].
  void _validateLinkedLibrary(LinkedLibrary linkedLibrary) {
    for (LinkedUnit unit in linkedLibrary.units) {
      for (LinkedReference reference in unit.references) {
  