Unit Testing

Quick Question: How would you do unit tests on this function? ```
async function submit() {
        setIsSubmitting(true);

        if (!isConnected){
            setDisplayToast(true);
            setToastMessage("Please check your connection and try again.");
            setToastMsgLines(1);
            setToastColor(colors.danger);
            setTimeout(() => {
                setDisplayToast(false);
                setIsSubmitting(false);
            }, 3600);
            return ;
        }

        console.log("Signing in...");

        // Sign in with Supabase
        const { error } = await supabase.auth.signInWithPassword({
            email: form.email,
            password: form.password,
        })

        // Handle sign in failure
        if (error){
            console.log(error.status);
            console.log(error.message);
            if (error.name = "invalid_credentials"){
                setDisplayToast(true);
                setToastMessage("Invalid email or password. Please try again.");
                setToastMsgLines(1);
                setToastColor(colors.danger);
                setFormWarn(true);
                setTimeout(() => {
                    setDisplayToast(false);
                }, 3600);
                setTimeout(() => {
                    setFormWarn(false);
                }, 1000);
            } else if (error.name = "email_not_confirmed"){
                setDisplayToast(true);
                setToastMessage("Please confirm your email address first.");
                setToastMsgLines(1);
                setToastColor(colors.danger);
                setFormWarn(true);
                setTimeout(() => {
                    setDisplayToast(false);
                }, 3600);
                setTimeout(() => {
                    setFormWarn(false);
                }, 1000);
            } else if (error.status == 429){
                setDisplayToast(true);
                setToastMessage("There is a problem logging you in. Please come back in a few minutes.");
                setToastMsgLines(2);
                setToastColor(colors.danger);
                setFormWarn(true);
                setTimeout(() => {
                    setDisplayToast(false);
                }, 3600);
                setTimeout(() => {
                    setFormWarn(false);
                }, 1000);
            }

            // Re-activate submit button
            setTimeout(() => {
                setIsSubmitting(false);
            }, 3600);
        } else {
            setIsSubmitting(false);

            // Load database data and redirect to home page once logged in.
            setIsOpening(true);

            console.log("Getting data from database:");

            // Get database data
            const fiberBreakdown = await getFiberBreakdownByGrade();
            setFiberBreakdownDB(fiberBreakdown);

            const fibersScanned = await getFibersScannedDaily();
            setFibersScannedDB(fibersScanned);

            const systemStatus = await getSystemStatusDatabase();
            setSystemStatusDB(systemStatus);

            const fiberLogs = await getFiberLogs();
            setFibersScanLogsDB(fiberLogs);

            // Store last update time
            await storeLastDatabaseUpdateTime();

            setIsOpening(false);

            router.replace("(main_app)/home");
        }
    }```