Testing

A file ending _test.sword beside your code holds its tests, and shield test finds them:

package strings

import "std/testing"

func TestTrimSpace(mut t *testing.T) !void {
    t.Equal(TrimSpace("  ada  "), "ada")
}

$ shield test std/strings
ok    6 tests  (0ms)

Nothing registers a test: the name is enough. Testing is the rest of it.