Proposal: rename assertion to test

[fantix]

Motivations

• assert_*() no longer panics, returning a test-specific Result[Unit, String] now.

  I remember the @assertion package was added to the stdlib before tests were switched to return Results. This indicates the assert_*() functions are not "assertions" that don't get in the way of non-test user code. Now the users have to handle the Results properly in production code, especially to deal with the String errors.

  With that said, a "proper" assertion would have to be like:

  @assertion.assert_eq(1, 1).unwrap()
  

  However, this explicitness of unwrap() defeats the idea of calling the package @assertion.

• There is no way to turn off assertions.

  This is debatable - Java and Python provide options to turn off assertions at runtime, C/C++ could use some macro tricks, and Rust disallows turning off std::assert calls but provides std::debug_assert that is excluded in release builds. The @assertion package in MoonBit looks more like a testing library to me, especially since it covers eq, ne, true, false, and likely more to add.

  In addition, we could borrow debug_assert from Rust that 1) panics if evaluated false, 2) is excluded from release builds, 3) does not live in the @assertion (or @test) package, and 4) has no siblings like eq, ne and so on.

• @assertion.assert... is redundant to type.

  Typing @test.assert_eq() feels much more natural than repeating the "assert" word twice.

[Yoorkin]

@test.assert_eq(a,b)?
@test.assert_is_not(a,b)?

or

@test.eq(a,b)?
@test.is_not(a,b)?

looks good to me, but the test is a keyword of MoonBit.
So I would prefer to use another package name to replace assertion, if a suitable one exists.

[zxch3n]

You may use https://github.com/zxch3n/moon-expect

Example Usage

expect("hello").equal("hello")
expect("hello").not().equal("hello") // abort
expect("hello").equal("hello1") // abort
expect("hello").not().equal("hello1") 

let a : Option[Int] = Some(1)
let b : Option[Int] = None
expect(a).to_be_some() 
expect(b).to_be_none() 

expect("hello").to_have_length(5)
expect("hello").not().to_have_length(6)

expect(1).to_be_less_than(4)

let a : Result[Int, Int] = Ok(1)
let b : Result[Int, Int] = Err(1)
expect(a).to_be_ok()
expect(b).to_be_err()

expect(1.0).close_to(1.0, 0.1)

Example Error Messages

AssertionError: expected 1.0 to be close to 1.2 (±0.1)

- Expected: 
+ Received: 

- 1.2
+ 1.0

AssertionError: expected "hello" to equal "hello1"

- Expected: 
+ Received: 

- "hello1"
+ "hello"

I'd love to make it support something like debug_assert if possible.

[bobzhang]

Note test is a keyword in MoonBit, but @test.eq also works, the name test does look better.

Any other thoughts?

[Yoorkin]

The package @assertion has been renamed to @test. The names of the testing functions have also changed to eq ne ... is_true. #609