message: Add mockImporter builder util
diff: @@ -63,3 +63,13 @@ export const MODULE_TEMPLATE = [
  export function noopImporter() {
  return null;
  }
  +
  +/**
  + * Builds an importer where the keys are import paths and the values are AST nodes
  + */
  +export function makeMockImporter(mocks = {}) {
  + return path => {
  + const source = path.node.source.value;
  + return mocks[source];
  + };
  +}
  