Uncaught Error: Module build failed: TypeError: Cannot read property 'afterCompile' of undefined

I followed the instructions for setting up testing on my Ionic project, but I got the error `Uncaught Error: Module build failed: TypeError: Cannot read property 'afterCompile' of undefined`

After some investigation I realized that Ionic uses webpack 3, but the default version of `ts-loader` installed with npm install is for webpack 4. Please update the blog entry to install a 3.x.x version of ts-loader.

For anyone facing this error you can simply install the correct version of ts-loader manually like this...

```
npm uninstall -D ts-loader
npm install -D ts-loader@3.x.x
```

Inspect the blog entry covering testing setup and its dependency-install instructions. Confirm that it describes the webpack 3 and ts-loader compatibility issue, then update the entry to recommend a 3.x.x version of ts-loader; the work is done when the documented setup avoids the reported afterCompile error.

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