Go Test Quality

Tests are production code. They run in CI on every commit, they document behavior, and they're the first thing you read when a function breaks at 3am. Write them with the same care you'd give to code that handles money.

1. Test Design Philosophy

Test behavior, not implementation

// ✅ Good — tests what the function DOES
func TestTransferFunds_InsufficientBalance(t *testing.T) {
    from := NewAccount("alice", 100)
    to := NewAccount("bob", 0)

    err := TransferFunds(from, to, 150)

    require.ErrorIs(t, err, ErrInsufficientFunds)