anchor.diff:    }
   }
   
  -Future<Null> basicTest(Map<String, String> sourceFiles, String entryPoint,
  -    bool strong, List<String> invalidate, Directory outDir) async {
  +Future<Null> basicTest(YamlMap sourceFiles, String entryPoint, bool strong,
  +    YamlList invalidate, Directory outDir) async {
     Uri entryPointUri = outDir.uri.resolve(entryPoint);
  -  Set<String> invalidateFilenames = invalidate?.toSet() ?? new Set<String>();
  +  Set<String> invalidateFilenames =
  +      invalidate == null ? new Set<String>() : new Set<String>.from(invalidate);
     List<Uri> invalidateUris = <Uri>[];
     Uri packagesUri;
     for (String filename in sourceFiles.keys) {
  
positive.code: import "package:testing/testing.dart"
      show Chain, ChainContext, Result, Step, TestDescription, runMe;
  
  import "package:yaml/yaml.dart" show YamlMap, loadYamlNode;
  
  import "incremental_utils.dart" as util;
  
  
negative.code: }
  
  void performErrorAndWarningCheck(
      YamlMap world,
      bool gotError,
      List<String> formattedErrors,
      bool gotWarning,
  