```py
DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(n*t0, t0)], 'Tfuncs': [Lambda(i, exp(n*i))]})
assert integrate_hyperexponential(Poly(t0, t0), Poly(1, t0), DE) == (Piecewise((x, Eq(n, 0)), (exp(n*x)/n, True)), 0, True)
```