feat(nix/runTestsuite): add runTestsuite

This is a very simple test suite for nix expressions.
It should help us set up a good suite of unit tests for our nix-based
stuff.

Since we allow import from derivation, these tests can also depend on
derivations and e.g. use `builtins.readFile` to check outputs.

This is a first PoC to get us going, we can always replace it by
something different in the future if we don’t like it.

Change-Id: I206c7b624db2b1dabd9c73ffce4f87e658919958
Reviewed-on: https://cl.tvl.fyi/c/depot/+/662
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: tazjin <mail@tazj.in>
This commit is contained in:
Profpatsch 2020-06-27 22:56:58 +02:00
parent e2c7e38934
commit c8e888c1d2

View file

@ -0,0 +1,121 @@
{ lib, pkgs, depot, ... }:
# Run a nix testsuite.
#
# The tests are simple assertions on the nix level,
# and can use derivation outputs if IfD is enabled.
#
# You build a testsuite by bundling assertions into
# “it”s and then bundling the “it”s into a testsuite.
#
# Running the testsuite will abort evaluation if
# any assertion fails.
#
# Example:
#
# runTestsuite "myFancyTestsuite" [
# (it "does an assertion" [
# (assertEq "42 is equal to 42" "42" "42")
# (assertEq "also 23" 23 23)
# ])
# (it "frmbls the brlbr" [
# (assertEq true false)
# ])
# ]
#
# will fail the second it group because true is not false.
let
inherit (depot.nix.yants) sum struct string any unit defun list;
# rewrite the builtins.partition result
# to use `ok` and `err` instead of `right` and `wrong`.
partitionTests = pred: xs:
let res = builtins.partition pred xs;
in {
ok = res.right;
err = res.wrong;
};
# The result of an assert,
# either its true (yep) or false (nope).
# If its nope, we return the left and right
# side of the assert, together with the description.
AssertResult =
sum "AssertResult" {
yep = struct "yep" {
test = string;
};
nope = struct "nope" {
test = string;
left = any;
right = any;
};
};
# Result of an it. An it is a bunch of asserts
# bundled up with a good description of what is tested.
ItResult =
struct "ItResult" {
it-desc = string;
asserts = list AssertResult;
};
# assert that left and right values are equal
assertEq = defun [ string any any AssertResult ]
(desc: left: right:
if left == right
then { yep = { test = desc; }; }
else { nope = {
test = desc;
inherit left right;
};
});
# Annotate a bunch of asserts with a descriptive name
it = desc: asserts: {
it-desc = desc;
inherit asserts;
};
# Run a bunch of its and check whether all asserts are yep.
# If not, abort evaluation with `throw`
# and print the result of the test suite.
#
# Takes a test suite name as first argument.
runTestsuite = defun [ string (list ItResult) unit ]
(name: itResults:
let
goodAss = ass: {
good = AssertResult.match ass {
yep = _: true;
nope = _: false;
};
x = ass;
};
goodIt = it: {
inherit (it) it-desc;
asserts = partitionTests (ass:
AssertResult.match ass {
yep = _: true;
nope = _: false;
}) it.asserts;
};
goodIts = partitionTests (it: (goodIt it).asserts.err == []);
res = goodIts itResults;
in
if res.err == []
then {}
# TODO(Profpatsch): pretty printing of results
# and probably also somewhat easier to read output
else throw
( "testsuite ${name} failed!\n"
+ lib.generators.toPretty {} res));
in {
inherit
assertEq
it
runTestsuite
;
}