Avoid duplicate code testing c++

I write some unit tests and I want to avoid duplicate code. Say I have a Scenario1 defined in the following way:

SCENARIO("Scenario1") {
    cfg config;
    config.field = 0;

    GIVEN("something_1") {    
        WHEN("event_1") {
            //block_code_1
        }

        WHEN("event_2") {
            //block_code_2
        }

        WHEN("event_3") {
            //block_code_3
        }
    }
}

Now, Scenario2 is the same as Scenario1, but config.field = 1 and block_code_1 and block_code_2 are the same except for block_code_3 which is different in Scenario2.

So my question is: what is the best practice to do unit-testing in this case ?