Integration of heaviside function

Hello, the picture is the result of code: ezplot(heaviside(Myfunction(x)), [-0.9, 0.9])

I want to calculate the area bounded by the result and y=0

So I enter the code: integral(@(x) heaviside(Myfunction(x),-0.9,0.9) but the result is 0

If I enter: integral(@(x) heaviside(Myfunction(x),-0.00000001,0.0000001) the result has value 6*10^-8

Can anybody explain why this happen and how should I calculate the area ? Thanks.