assert: display better error message for assertion

[SgtPooki]

This commit makes understanding assertion failures easier by
displaying the values that failed the assertion.

Changes the error message from

➜ node git:(fixTestMsg) ✗ tools/test.py parallel/test-zlib-random-byte-pipes.js
=== release test-zlib-random-byte-pipes ===
Path: parallel/test-zlib-random-byte-pipes
assert.js:45
throw new errors.AssertionError({
^

AssertionError [ERR_ASSERTION]: hashes should match
at HashStream.out.on.common.mustCall (/Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js:154:10)
at HashStream. (/Users/dempser/code/node/test/common/index.js:517:15)
at emitOne (events.js:115:13)
at HashStream.emit (events.js:210:7)
at HashStream.end (/Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js:139:10)
at Gunzip.onend (_stream_readable.js:596:10)
at Object.onceWrapper (events.js:314:30)
at emitNone (events.js:110:20)
at Gunzip.emit (events.js:207:7)
at endReadableNT (_stream_readable.js:1052:12)
Command: out/Release/node /Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js
[00:00|% 100|+ 0|- 1]: Done

to

➜ node git:(fixTestMsg) tools/test.py parallel/test-zlib-random-byte-pipes.js
=== release test-zlib-random-byte-pipes ===
Path: parallel/test-zlib-random-byte-pipes
assert.js:45
throw new errors.AssertionError({
^

AssertionError [ERR_ASSERTION]: Hash 'some non hash' equals '4663ea81710e8f7941232a9f46a99e11118f336d'.
at HashStream.out.on.common.mustCall (/Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js:154:10)
at HashStream. (/Users/dempser/code/node/test/common/index.js:517:15)
at emitOne (events.js:115:13)
at HashStream.emit (events.js:210:7)
at HashStream.end (/Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js:139:10)
at Gunzip.onend (_stream_readable.js:596:10)
at Object.onceWrapper (events.js:314:30)
at emitNone (events.js:110:20)
at Gunzip.emit (events.js:207:7)
at endReadableNT (_stream_readable.js:1052:12)
Command: out/Release/node /Users/dempser/code/node/test/parallel/test-zlib-random-byte-pipes.js
[00:00|% 100|+ 0|- 1]: Done

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

[Trott]

LGTM. It might be even better to remove the message entirely and use the default message from assert.strictEqual().

[Trott]

CI: https://ci.nodejs.org/job/node-test-pull-request/10502/

[Trott]

Landed in beb2357.
Thanks for the contribution! 🎉

[gibfahn]

This is actually not quite correct (although it was equally wrong before 😁 ). The message is displayed if the assert fails, which only happens when the two values are not equal to each other.

@SgtPooki if you could push a commit that just removes the message altogether (making it assert.strictEqual(c, inp._hash); that would be really helpful.

[SgtPooki]

I can, but assertion errors are typically worded similarly to commit messages: active present voice. The error message says "assertion error: msg" the error is that hashes should equal.

The default message shows "assertion error: Val1 === val2" which is the same thing but without context.

I decided to go with the custom message because I thought that mentioning they should be hashes was more helpful than the default.