sys::Test.verifyErr is great for testing that a specific Err is thrown, but I always find myself taking the test one step further and verifying the Msg in the Err. It's something I do in all my projects and as such, my test superclasses always has the following:

Void verifyErrMsg(Type errType, Str errMsg, |Test| c) {
    try {
        c.call(this)
    } catch (Err e) {
        if (!e.typeof.fits(errType)) 
            verifyEq(errType, e.typeof)
        verifyEq(errMsg, e.msg)
        return
    }    
    fail("$errType not thrown")
}

Typical usage in a test would be:

Void testMeltdown() {
    reactor := iocRegistry.serviceById("NuclearReactor")
    
    verifyErrMsg(DangerErr#, "Thermonuclear meltdown imminent") {
        reactor.shutdown()
    }
}

If others do similar then it may be worth considering adding it to Test.

Also, what of having a verifyTrue()??? I know I'm supposed to use verify() but given there's a verifyFalse() I always feel cheated that there's not a opposing verifyTrue()! I find myself typing it a lot, and then I have to correct it. Plus it looks strange nestled in-between the false statements:

verifyFalse(aThis)
verify     (aThat)
verifyFalse(aOther)

I'm not saying delete verify(), just add a pseudonym for it. (I'm usually against having 2 differently name methods that do the same thing - but I can make an exception in this case!)

I really like verifyErrMsg - great idea.

I am not super keen on verifyTrue, but its only a line of code. So I don't have a big problem with it.

If you are interested in implementing send me the patch

Okay, will do!