Prevent network requests during test run

I just noticed that whenever I run my test suite that network requests are going out for Gravatar images.

Specifically, I have a component integration test that renders a template with the 'htmlbars-inline-precompile' method.

A child component that gets rendered as a result of this call to this.render() contains the Gravatar component.

Is there any way to disable network requests during a test run?