How to test various exit codes in Golang?

A function has been created that returns depending on the input a 0, 1, 2 or 3 exit code. In order to avoid that the code needs to be build and manually tested every time the code changes a test is required.

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Aim: to test different exit codes in Golang

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Attempts

Attempt one

Neither the code samples of this nor this Q&A answers this question.

Attempt two

func ExitCodeOne() {
    fmt.Println("Exit code 1")
    os.Exit(1)
}

results in:

Your username is "bla2".Your username is "bla3".Exit code 1
FAIL    tool    0.012s

as the exit code 1 causes the whole test to fail.

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Problem

At the moment the following problems are experienced:

1. How to get the exit code?
2. How to prevent that the exit code 1 let the test fail
3. How to compare the actual exit code with the expected exit code?

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Desired answer

A test that is able to compare the actual exit code with the expected exit code is desired, e.g.:

func TestArgs(t *testing.T) {
    ExitCodeOne()

    actual:=<current_exit_code_to_string>
    expected:=1

    if actual != expected {
        t.Errorf("Test failed, expected: '%s', got:  '%s'", expected, actual)
    }
}