createCoverageReport(type: ReportType, data: CoverageMapData | CoverageMap) {
    let map: CoverageMap;

    if (isCoverageMap(data)) {
      map = data;
    } else {
      map = createCoverageMap(data);
    }

    const transformed = this.executor.sourceMapStore.transformCoverage(map);

    const context = createContext({
      dir: this.directory,
      sourceFinder: transformed.sourceFinder,
      watermarks: this.watermarks
    });
    const tree = summarizers.pkg(transformed.map);
    const report = create(type, this.getReporterOptions());
    tree.visit(report, context);
  }

  async onRunComplete(
    contexts: Set<Context>,
    aggregatedResults: AggregatedResult,
  ) {
    await this._addUntestedFiles(this._globalConfig, contexts);
    const {map, sourceFinder} = this._sourceMapStore.transformCoverage(
      this._coverageMap,
    );

    try {
      const reportContext = istanbulReport.createContext({
        dir: this._globalConfig.coverageDirectory,
        sourceFinder,
      });
      const coverageReporters = this._globalConfig.coverageReporters || [];

      if (!this._globalConfig.useStderr && coverageReporters.length < 1) {
        coverageReporters.push('text-summary');
      }

      const tree = istanbulReport.summarizers.pkg(map);
      coverageReporters.forEach(reporter => {
        tree.visit(istanbulReports.create(reporter, {}), reportContext);
      });
      aggregatedResults.coverageMap = map;
    } catch (e) {
      console.error(
        chalk.red(`
        Failed to write coverage reports:
        ERROR: ${e.toString()}
        STACK: ${e.stack}
      `),
      );
    }

    this._checkThreshold(this._globalConfig, map);
  }

	summarizers,
	Watermarks
} from 'istanbul-lib-report';

import { CoverageMap } from 'istanbul-lib-coverage';

const watermarks: Watermarks = {
	statements: [],
	branches: [],
	functions: [],
	lines: []
};

createContext();
createContext({});
const context = createContext({
	dir: 'foo',
	watermarks,
	sourceFinder: (filepath: string) => ''
});

context.watermarks;
context.sourceFinder('foo').trim();

const defaultMarks: Watermarks = getDefaultWatermarks();

const map = new CoverageMap({});
summarizers.flat(map).getRoot();
summarizers.nested(map).getRoot();
summarizers.pkg(map).getRoot();