Show expected and actual values for assertion failures

user_1634372 0
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When writing assertions for my tests, the assertion failures don't provide enough information without needing to open an IDE and start debugging.

For example, I have some code that uses the 'assert' library:

import * as assert from 'assert'

// some code

assert(someObject.getValue() === 0)

I just get

       AssertionError [ERR_ASSERTION]: false == true
           + expected - actual

           -false
           +true

This error message isn't really meaningful. As a workaround, I added it in the message in the assertion:

assert(someObject.getValue() === 0, 
       '\nActual: ' + someObject.getValue() + 
       '\nExpected: ' + 0)

Is there a better, cleaner way to just show the expected & actual values without overriding the message on every assertion? I also tried to create an assert wrapper, but I wasn't able to extract the actual and expected values from the expression.

EDIT: assert.strictEqual resolves this issue for equalities only. But as soon as any other operator is included, then we have the same issue (e.g. assert(someObject.getValue() > 0)

Any advice would be appreciated.

Thanks!

typescript node.js assert
1 Answers

You can use assert.strictEqual(actual, expected[, message]) to get actual/expected error messages without the need of the third message argument:

assert.strictEqual(someObject.getValue(), 0)

You'd get an error message such as:

// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:
//
// 1 !== 0

Hopefully that helps!

user_50596570
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