Testing a Deploy transaction with an invalid verify function signature

[YaronWittenstein]

Each valid Template under SVM needs to have the svm_verifymethod and it should have () -> (i32) function signature

(module
  (export "svm_verify" (func $svm_verify))

  ;; Valid `svm_verify` signature
  (func $svm_verify (result i32)
    (i32.const 0)))

This time we want to feed Deploy with an invalid svm_verify input.
We'd expect ValidateDeploy to fail.

There are two options to generate such an input:

Modify the SDK code-generation

The current SDK's code at the point of writing this issue generates an empty verify.
https://github.com/spacemeshos/svm/blob/22fb1cf627d5c82d20c285744dd9ee708e9c7c08/crates/sdk-macros/src/template.rs#L283

Thus, the current verify code-generation is a stopgap since authors of Template will have to write their own verify.
Probably, the best thing will be to remove this stub and enforce each template to have svm_verify created.

I think that the elegant way will be to add a #[verify] decorator for such a method (similar to the #[ctor] and #[endpoint]) and let the compiler take care of generating svm_verify at the final Wasm.

Note: the compiler needs to enforce only one (and exactly one) method that could be annotated with the #[verify] attribute within a Template.

Write Wasm Manually

That is also a valid option, but it might be a bit harder but still feasible. For example, we can manually compose a Wasm file in its Text representation and convert a binary Wasm.

Then we can manually create a JSON for the Template Metadata (empty Data layout and pick a ctor).
Finally, we could stitch the pieces using the CLI.

Other

Once we have a working test, it should be easy to test an invalid svm_alloc method and other required SVM Template functions (more due to the Nonces Schemes).