Introduce the Test.assertEqual function

[m-Peter]

Closes onflow/cadence-tools#93

Description

This function has built-in support for showing the difference between the expected and the actual value. For example:

Test results: "tests/test_foo_contract.cdc"
- FAIL: testGetIntegerTrait
		Execution failed:
			error: assertion failed: not equal: expected: "Hugee", actual: "Huge"
			  --> 7465737400000000000000000000000000000000000000000000000000000000:27:8
			
- PASS: testAddSpecialNumber
Coverage: 95.7% of statements

---

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov]

Codecov Report

Merging #2571 (e77dffe) into master (1c6994f) will increase coverage by 0.00%.
The diff coverage is 89.47%.

@@           Coverage Diff           @@
##           master    #2571   +/-   ##
=======================================
  Coverage   78.54%   78.55%           
=======================================
  Files         336      336           
  Lines       77666    77704   +38     
=======================================
+ Hits        61005    61042   +37     
+ Misses      14386    14384    -2     
- Partials     2275     2278    +3     

Flag	Coverage Δ
unittests	78.55% <89.47%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
runtime/stdlib/test_contract.go	87.88% <89.47%> (+0.07%)	⬆️

... and 1 file with indirect coverage changes

[turbolent]

Nice!

[kozlovb]

I wonder if equality of two types could be enforced easily.

By that I mean that if types are not equal then the very first test execution is not going to pass anyway. So, its not something that important. On the other hand having comparisons of ints to strings fail at the compile time could've been nice too.

Also, may be there is already a check at the compile time that I've missed.

[m-Peter]

import Test

pub fun test() {
	Test.assertEqual(true, 1)
}

We have such a test, and the assertion error is the following:

assertion failed: not equal: expected: true, actual: 1

But since the assertEqual method should work for any sub-type of AnyStruct, this is the expected behavior.

On the other-hand, for types that do not support equality, e.g resources, we also have a test case:

import Test

pub fun test() {
	let f1 <- create Foo()
	let f2 <- create Foo()
	Test.assertEqual(<-f1, <-f2)
}

pub resource Foo {}

And it fails with:

errs := checker.RequireCheckerErrors(t, err, 2)
assert.IsType(t, &sema.TypeMismatchError{}, errs[0])

[kozlovb]

Right, cadence is interpreted language, my bad.

Great, that you've covered that in test. "not equal: expected: true, actual: 1" as discussed in PMs may be error message can specify that types differ.

[kozlovb]

Although, commit is merged and I think this point is "matter of taste"/minor. So, fine for me either way.

[m-Peter]

Great, thanks for pointing it out though 🙌

[m-Peter]

All good!