anchor.diff:          StdioProcess process;
           try {
             var args = <String>[];
  +          if (experimentalFlags[ExperimentalFlag.nonNullable]) {
  +            args.add("--null-safety");
  +          }
             args.add(generated.path);
             process = await StdioProcess.run(context.vm.toFilePath(), args);
             print(process.output);
  
positive.code: const String experimentalFlagOptions = '--enable-experiment=';
  
  class TestOptions {
    final Map<ExperimentalFlag, bool> experimentalFlags;
    final bool forceLateLowering;
    final bool forceNnbdChecks;
    final bool forceNoExplicitGetterCalls;
    final bool nnbdAgnosticMode;
    final String target;
  
    TestOptions(this.experimentalFlags,
        {this.forceLateLowering: false,
        this.forceNnbdChecks: false,
        this.forceNoExplicitGetterCalls: false,
  
negative.code: 
    Map<ExperimentalFlag, bool> computeExperimentalFlags(
        Map<ExperimentalFlag, bool> forcedExperimentalFlags) {
      Map<ExperimentalFlag, bool> flags = new Map.from(defaultExperimentalFlags);
      flags.addAll(_experimentalFlags);
      flags.addAll(forcedExperimentalFlags);
      return flags;
    }
  