content-type test doesn't work in chapter "Integration tests"

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https://docs.deepkit.io/german/framework.html#_integration_tests

expect(response.getHeader('content-type')).toBe('text/plain; charset=utf-8');

the delivered content-type is undefined

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and the body has "hello world" in it (including ")

maybe

return new Response('hello ' + text, 'text/plain; charset=utf-8');