It’s because you are not writing the top level test correctly - there is no
testing at all !
> On Mar 18, 2020, at 7:02 AM, Ondrej <ondrej.ko...@gmail.com> wrote:
>
>
> Hey!
>
> There's an issue I've been grappling with for ages - say I have a custom
> function, Print, that calls six other functions, FormatString, FormatBool,
> FormatXYZ, ..., and I have no tests. Once I write some basic tests for Print,
> it does call some of the other functions and from looking at my test
> coverage, it looks like I have those nested functions covered, but I never
> called them explicitly, I never did try all their corner cases, did not fuzz
> them or anything.
>
> It may sound odd or not important, but I have encountered this in almost
> every project in Go and other languages - the setup is always the same - lots
> of small functions doing their thing and then some orchestrator that
> integrates everything (could be a cli, could be an endpoint etc.) and once I
> set that up, coverage spikes up.
>
> Here's a simple example:
>
> // calculator.go
> package calculator
>
> func Add(a, b int) int {
> return a+b
> }
>
> func Calculator(a, b int) int {
> return Add(a, b)
> }
>
> // calculator_test.go
> package calculator
>
> import "testing"
>
> func TestCalculator(t *testing.T) {
> s := Calculator(1, 2)
> _ = s
> }
>
> In this case, Calculator is covered, and so is Add, but I never tested how
> Add behaves for values close to the int maximum and with other potentially
> dangerous edge cases.
>
> I've though about this over the years a tiny bit and never really found a
> great solution, because it's not really a technical thing, it's more about
> the workflow and attitude to testing.
>
> I prototyped a simple tool that looks up all the exported functions and
> methods in a package and then checks if they are *explicitly* called in our
> tests. This does not guarantee anything, but at least we know they were
> explicitly used, not indirectly called within a different function. The
> prototype does not quite work for methods, because I got kind of lost in the
> go/{parser,ast} indirections. Also reassigning functions as first class
> values and then calling them from a different variable will probably also
> break it.
>
> So it does give a lot of false positives for methods, but should be mostly
> fine for functions.
>
> While it probably does not solve any problems for any people apart from me,
> I'll try and fix the method issues, because I do really need it for my own
> test writing.
>
> Do let me know if there's a better solution to this or if you've encountered
> this and have some thoughts on the topic.
>
> Thanks!
>
> Ondrej
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> <main.go>
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