Add macro for generating individual test functions per testscript file

[imjasonh]

Feature Request: Test Generator Macro

Currently, users run all testscripts in a directory with:

testscript::run("testdata").execute().unwrap();

This is similar to Go's testscript.Run(t, testscript.Params{Dir: "testdata"}), but Go also supports running individual test cases with go test -run=TestFoo/name_of_test.

Proposed Solution

Add a procedural macro that generates individual Rust test functions for each .txt file:

// In tests/testdata_tests.rs
testscript_rs::generate_tests!("testdata");

This would generate:

#[test] fn test_hello_txt() { testscript::run_single("testdata/hello.txt").execute().unwrap(); }
#[test] fn test_exists_txt() { testscript::run_single("testdata/exists.txt").execute().unwrap(); }
// etc. for each .txt file

Benefits

• Individual test execution: cargo test test_hello_txt
• Parallel test discovery: Each file shows up as a separate test in IDEs
• Better test reporting: Failures are isolated to specific files
• Rust ecosystem compatibility: Works with cargo test filtering

Technical Approach

• Procedural macro that reads the directory at compile time
• Generates test functions with sanitized names (replace - and . with _)
• Each generated test calls a run_single function for individual file execution
• Handle expected failures gracefully (some testdata files contain unsupported commands)

This would make testscript-rs even more idiomatic for Rust developers while maintaining the simple API for running all tests together.