The key to making apps that work is to be constantly testing what you make. Really. Test every little feature as you add it. Nothing is worse than having pages of blocks that you think work and then having to pull it all apart when you have an error hiding somewhere in the churning code.
If you write a feature that depends on other pieces to be written before you test it, you might try to get away without testing it. That’s a bad move. Figure out a way to test the feature independently of the others. Then you can move forward with confidence.