Requesting HBS page, got 500 HTTP error and "partials not found" message

Hello,
when I run supertest request over an handlebars page that includes some partials I get a 500 server error, with message "partial ... not found". Removing the partial from the handlebars template everything works in the test request.

Please note that actually the partial is there, when I invoke the same URL of the request manually (browser) I get a 200 with the partial included in the page.

```
supertest(runningExpressApp)
.get('/myPageWithPartials')
.expect('Content-Type', /html/)
.expect(200)
.then((res) => {
//never come here because of error "partial not found"
});
```
Any suggestion? Thanks, F.