Test methods fail using Storage. Illuminate\Http\Testing\imagepng() in Laravel
I recently ran into this problem and installed PHP GD Extension
Here's the code I placed in my Dockerfile
RUN apt-get update && \ apt-get install -y \ libzip-dev \ libjpeg62-turbo-dev \ libpng-devRUN docker-php-ext-install gd
Note: Installing gd requires that you have libzip, libpng e.t.c