BDD in go, updated code from @zer0tonin / blog post https://alicegg.tech/2019/03/09/gobdd.html

account.feature

Feature: bank account
  A user's bank account must be able to withdraw and deposit cash
  Moreover, as the user is rich, with a very large estate, and a lot of vast networking,
  The bank tolerates having an overdrawn account, thank to expensive overdraft charges

  Scenario Outline: Deposit
    Given I have a bank account with <start>$
    When I deposit <deposit>$
    Then it should have a balance of <end>$
    
    Examples:
      | start | deposit | end |
      | 10    | 0       | 10  |
      | 10    | 10      | 20  |
      | 100   | 50      | 150 |
      | -100  | 50      | -50 |

  Scenario Outline: Withdrawal
    Given I have a bank account with <start>$
    When I withdraw <withdrawal>$
    Then it should have a balance of <end>$

    Examples:
      | start | withdrawal | end  |
      | 10    | 0          | 10   |
      | 20    | 10         | 10   |
      | 100   | 50         | 50   |
      | 100   | 500        | -400 |

account.go

package bank

type account struct {
	balance int
}

func (a *account) deposit(amount int) {
	a.balance = a.balance + amount
}

func (a *account) withdraw(amount int) {
	a.balance = a.balance - amount
}

account_test.go

package bank

import (
	"fmt"

	"github.com/cucumber/godog"
)

var testAccount *account

func iHaveABankAccountWith(balance int) error {
	testAccount = &account{balance: balance}
	return nil
}

func iDeposit(amount int) error {
	testAccount.deposit(amount)
	return nil
}

func iWithdraw(amount int) error {
	testAccount.withdraw(amount)
	return nil
}

func itShouldHaveABalanceOf(balance int) error {
	if testAccount.balance == balance {
		return nil
	}
	return fmt.Errorf("Incorrect account balance, I got %d, I wanted %d", testAccount.balance, balance)
}

func InitializeScenario(ctx *godog.ScenarioContext) {
	// Add negative tests
	ctx.Step(`^I have a bank account with (\-*\d+)\$$`, iHaveABankAccountWith)
	ctx.Step(`^I deposit (\d+)\$$`, iDeposit)
	ctx.Step(`^I withdraw (\d+)\$$`, iWithdraw)
	ctx.Step(`^it should have a balance of (\-*\d+)\$$`, itShouldHaveABalanceOf)
}

go.mod

module bank

go 1.18

require github.com/cucumber/godog v0.12.5

require (
	github.com/cucumber/gherkin-go/v19 v19.0.3 // indirect
	github.com/cucumber/messages-go/v16 v16.0.1 // indirect
	github.com/gofrs/uuid v4.2.0+incompatible // indirect
	github.com/hashicorp/go-immutable-radix v1.3.1 // indirect
	github.com/hashicorp/go-memdb v1.3.3 // indirect
	github.com/hashicorp/golang-lru v0.5.4 // indirect
	github.com/spf13/pflag v1.0.5 // indirect
)