Checking, Testing, and Debugging

Feng currently separates semantic checking, user tests, and debugging into independent workflows.

Check a Project

feng check
feng check --format json

check always checks the entire resolved project rather than only a single .ff file passed on the command line. The path can be a project directory, a feng.fm file, or any file within a project; the tool searches upward for the nearest manifest.

Text output is intended for terminals. JSON output is suitable for editors and CI.

Write a Test Project

The CLI does not currently provide a feng test command. Tests can be written as a regular target: "bin" project using the std.test standard library package:

module app_test;

import std.test;

func main(args: string[]) {
  describe("math", () {
    test("addition", () {
      assert(1 + 1 == 2, "addition should produce two");
    });
  });
}

Run the tests as a regular program:

feng run

std.test also provides skip markers and assertEquals. A test project can declare the library under test as a local path dependency.

Debug with VS Code

After installing the Feng VS Code extension, create a Feng launch configuration in Run and Debug. The extension invokes feng dap --stdio and attempts to infer the program path and build task from the nearest target: "bin" manifest.

Local, non-release executable projects on macOS and Linux are currently supported. You can inspect breakpoints, stack frames, and variables. Watch and evaluate expressions support identifiers, member access, constant integer indexing, and simple arithmetic and comparison expressions, but not calls or assignments with side effects.

Diagnose Problems

When a build fails, investigate in this order:

Run feng check to obtain syntax and semantic diagnostics.
Run feng deps install --force to rule out a dependency cache problem.
Run feng clean, then build again.
Use feng --help or the relevant command's --help to verify its options.

The lexical, syntax, and semantic subcommands under feng tool are intended for advanced diagnostics and are not required in a normal project workflow.