Playground runs transform interface and your example runs minify only. (that's the reason it shows different output)

(this is off topic, but for the reference)

No idea why but this behavior is strictly copied from terser.

@Austaras The behavior doesn't really appear to strictly match terser from what I can see. If you use a longer string the problem is even more clear.

swc.minify produces:

const text="Some really long text that you definitely don't want to include twice because it's really long";console.log("Some really long text that you definitely don't want to include twice because it's really long");

Terser with the same settings produces the more reasonable output of:

const text="Some really long text that you definitely don't want to include twice because it's really long";console.log(text);

It doesn't ever really make sense to inline in this particular case because the variable is declared in the global scope and thus can't be dropped. As a result, any inlining is going to result in duplication. If you add the module: true option to both terser and swc, then you get consistent and sensible output where the string is inlined and only appears once:

console.log("Some really long text that you definitely don't want to include twice because it's really long");

This is because the variable test is now in module scope instead of being declared as a global and isn't observable outside of the module and can be safely removed. But the behavior for module: false is less than ideal.