Wildcards in tests

[kylegoetz]

Suppose I want to test a rule that parses variable names, but the top level of my file cannot have a variable name. Say variable names only appear four rules deep from the top level.

There isn't a straightforward way to do unit tests on just the variable name rule.

Something like

===
var name
===
foo = bar { baz ; fizz .
---
(fakelang
  (term_declaration
    (left_hand_side
      (symbol
        (var_name)))
    (equals)
    (rhs
      (and so on))))

The problem is that this test would fail if the rules term_declaration, left_hand_side, symbol, equals, rhs, and so on were to fail. Even if I changed one of those names (say left_hand_side became lhs), it would break tests intended to test something completely unrelated.

It would be really nice if I could write an expected test result using something like

---
(fakelang
  (* (var_name) *))

The motivation for this is that I have a lot of types of literals that I'd like to test the rules for, but the top level of my code can only be one of a few things, so all my literal tests are of the form

===
boolean literal
===
x = true
---
(unison
  (term_declaration
    (wordy_id)
    (equals)
    (boolean)))

First, this gets wordy to test one rule. Second, the thing that actually has made testing a pain in the butt, is if I decide a totally unrelated rule, currently called wordy_id, shoudl isntead be called name, it breaks every test for literals even though it has nothing to do with the rules I'm testing.

[kylegoetz]

Maybe instead you could identify the parent rule to "start with"? So then something like

---
x = true
---
[term_declaration] (wordy_id) (equals) (boolean)

That doesn't fix it for all cases, but it does let you ignore a lot of upstream boilerplate to get to what you're actually testing.

[extradosages]

Being able to write unit tests for sub-rules is key!

Maybe instead you could identify the parent rule to "start with"? So then something like

---
x = true
---
[term_declaration] (wordy_id) (equals) (boolean)

That doesn't fix it for all cases, but it does let you ignore a lot of upstream boilerplate to get to what you're actually testing.

This is the way to go ☝️.