t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected copies to be length %d, but was actually %d.",testNumber,expected,actual)
t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected message for copies datum #%d to be %q, but was actually %q.",testNumber,datumNumber,expected,actual)
t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected length of context for copies datum #%d to be %d, but was actually %d.",testNumber,datumNumber,expected,actual)
t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected context for copies datum #%d to have key %q, but didn't.",testNumber,datumNumber,expectedKey)
t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected value for context for copies datum #%d at key %q to have value [%v], but actually had [%v].",testNumber,datumNumber,expectedKey,expectedValue,actualValue)