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.