Prettify the stdlib testing framework

[jiribenes]

Motivation

I'm playing around a lot with the stdlib testing framework and it would be nice for it to be ever-so-slightly prettier. :)
I was very inspired by Bun when making this.

Features

Note

This PR might still need some refactoring before it gets merged. Nitpicks are welcome.
See Caveats below.

• string now has many more ANSI escapes for text formatting (bold, italic, etc.)
• test now has:
  • a tiny formatting interface using which we can turn all highlighting off (useful for CI / older terminals)
  • a few combinators for printing pretty text in bold, italic, etc.
  • a formatter for time durations in ms
• related: Add 'process' module with 'exit' function #541 enables a wrapper which makes everything much easier -- there we could make another one which does not use any formatting [= this is blocked on Add 'process' module with 'exit' function #541 which should get merged first]
• tests for test are now in stdlib/test instead of pos (which also means they don't run on MLton, I think)

Screenshots

Before:

After:

Caveats

• I don't quite like the ad-hoc formatting library: where could we move this?
  • Also, it is very ad-hoc: RESET deletes all formatting, which means that something like red("Hello " ++ bold("world") ++ "!") will actually result in <RED>Hello <BOLD>world<RESET>!<RESET>, so the exclamation mark is surprisingly no longer red.
• Can/should we move the Duration-related things into bench? EDIT: I've moved most of them except for diff
• Are we okay with ✓ and ✕ instead of + and -? Can we trust old terminals/CI with these?
• Should we handle Formatter straight-away or just expose it to the user and let them handle it?
• The timing needs to be opt-in only (= not in the CI version, sadly, since we're comparing text!) EDIT: Solved.

TODO

• from Add 'process' module with 'exit' function #541 by @b-studios: Another thought related to the design of suite and tests: would it make sense to first create a reified representation of the test results that can be queried to then render / print it / translate to exit code?

[jiribenes]

On one hand, I'd like to leave this split up, on the other, I'm a little worried that this doesn't get inlined.
The LLVM backend cannot even compile simple top-level constants (see #496), much less this :(

[b-studios]

I believe currently this will not be constant-folded. I think we should support top-level constants in LLVM for this to work; WDYT @phischu?

[jiribenes]

I'm fine with inlining the calls to escape and ++ here manually, but I'd still like #496. Otherwise this code is still unusable in LLVM.

[jiribenes]

Rebased on master after #541 got merged.

[jiribenes]

Unfortunately, this cool exiting runner is pretty useless if one of your files has multiple test suites (for example here is an example "in the wild").
In general, having multiple test suites is this testing framework's weak spot.

We could mandate suites and use them just for compartmentalisation/grouping, making a new runTests handler, but what if I really just want to write three tests and be done with it all?

[jiribenes]

Not sure if we want something like the ability to set tests as ignored/skipped when developing; it feels a little bit out of scope of this PR.
Nevertheless if we ever do want to support skips, here's a rough patch:

Patch for setting a test as skipped

diff --git i/libraries/common/test.effekt w/libraries/common/test.effekt
index c30f305c..28644bea 100644
--- i/libraries/common/test.effekt
+++ w/libraries/common/test.effekt
@@ -94,6 +94,7 @@ def assertEqual[A](obtained: A, expected: A) { equals: (A, A) => Bool } { show:
 interface Test {
   def success(name: String, duration: Int): Unit
   def failure(name: String, msg: String, duration: Int): Unit
+  def skipped(name: String): Unit
 }
 
 /// Runs the `body` as a test under the given `name`
@@ -114,6 +115,10 @@ def test(name: String) { body: => Unit / Assertion } = {
   }
 }
 
+/// Does *not* run the `body` as a test under the given `name`: 
+/// Useful for ignoring a test.
+def skip(name: String) { body: => Unit / Assertion } = do skipped(name)
+
 /// Run a test suite with a given `name`.
 /// - If `printTimes` is `true` (or missing), prints out time in milliseconds.
 /// - Formats automatically using ANSI escapes.
@@ -164,14 +169,26 @@ def suite(name: String, printTimes: Bool) { body: => Unit / { Test, Formatted }
         println("  " ++ msg.red)
         resume(())
       }
+
+      // 2c) Handle a skipped test
+      def skipped(name) = {
+        skipped = skipped + 1
+        println(("»" ++ " " ++ name).dim)
+        // no need to resume
+      }
     }
   }
 
+  val total = passed + failed + skipped
+
   // 3) Format the test results
   println("")
   println(" " ++ (passed.show ++ " pass").dimWhenZeroElse(passed) { green })
+  if (skipped > 0) { 
+    println(" " ++ (skipped.show ++ " skip").dim)
+  }
   println(" " ++ (failed.show ++ " fail").dimWhenZeroElse(failed) { red })
-  println(" " ++ (passed + failed).show ++ " tests total" ++ totalDuration.ms)
+  println(" " ++ total.show ++ " tests total" ++ totalDuration.ms)
 
   // 4) Return true if all tests succeeded, otherwise false
   return failed == 0

---

I find this interesting, since ideally, we would have some basic CLI args support for mainSuite, allowing it to run only certain tests (this way, we could have simple IDE support even to click & run all / click & run a single test).

[b-studios]

This is so nice, can't we just merge it?

Ah, I remember... Toplevel definitions.

ping @phischu

[jiribenes]

This would need #544, but we can fix that later, I'm fine with MLton support being rather second-class. :)

[jiribenes]

I don't know whether this should stay here or not: should it go into a different module?
(also see the code below)

[jiribenes]

Rebased on master after the newly merged #606.

[b-studios]