I think this is partially examined in this blog post and also answered here but i’m adding an adapted answer for your example:
Reusable code:
function sharedSetup(startPage) {
beforeEach(function() {
login_as_admin();
browser().navigateTo(startPage);
});
afterEach(function() {
logout();
});
};
How to use it:
describe('Services Page', function() {
sharedSetup('/services');
it('Some test for services page', function() {});
});
describe('Administrators Page', function() {
sharedSetup('/administrators');
it('Some test for administrators page', function() {});
});