test: add test

npm/webpack-preprocessor/index.ts

@@ -297,6 +297,10 @@ const preprocessor: WebpackPreprocessor = (options: PreprocessorOptions = {}): F
       // Seems to be a race condition where changing file before next tick
       // does not cause build to rerun
       Promise.delay(0).then(() => {
+        if (!bundles[filePath]) {
+          return
+        }
+
         bundles[filePath].deferreds.forEach((deferred) => {
           deferred.resolve(outputPath)
         })
@@ -386,6 +390,12 @@ preprocessor.__reset = () => {
   bundles = {}
 }
 
+// for testing purposes, but do not add this to the typescript interface
+// @ts-ignore
+preprocessor.__bundles = () => {
+  return bundles
+}
+
 function cleanseError (err: string) {
   return err.replace(/\n\s*at.*/g, '').replace(/From previous event:\n?/g, '')
 }

npm/webpack-preprocessor/test/unit/index.spec.js

@@ -91,7 +91,10 @@ describe('webpack preprocessor', function () {
       })
 
       it('runs webpack', function () {
+        expect(preprocessor.__bundles()[this.file.filePath]).to.be.undefined
+
         return this.run().then(() => {
+          expect(preprocessor.__bundles()[this.file.filePath].deferreds).to.be.empty
           expect(webpack).to.be.called
         })
       })