diff --git a/wallet/wallet.go b/wallet/wallet.go
index f2fb957..fca806e 100644
--- a/wallet/wallet.go
+++ b/wallet/wallet.go
@@ -16,6 +16,10 @@ func (w *Wallet) Deposit(amount Bitcoin) {
 	w.balance += amount
 }
 
+func (w *Wallet) Withdraw(amount Bitcoin) {
+	w.balance -= amount
+}
+
 func (w *Wallet) Balance() Bitcoin {
 	return w.balance
 }
diff --git a/wallet/wallet_test.go b/wallet/wallet_test.go
index c575ec9..65e764c 100644
--- a/wallet/wallet_test.go
+++ b/wallet/wallet_test.go
@@ -3,14 +3,22 @@ package wallet
 import "testing"
 
 func TestWallet(t *testing.T) {
-	wallet := Wallet{}
+	assertBalance := func(t testing.TB, wallet Wallet, want Bitcoin) {
+		t.Helper()
 
-	wallet.Deposit(10)
-
-	got := wallet.Balance()
-	want := Bitcoin(10)
-
-	if got != want {
-		t.Errorf("got %q want %q", got, want)
+		got := wallet.Balance()
+		if got != want {
+			t.Errorf("got %q want %q", got, want)
+		}
 	}
+	t.Run("deposit", func(t *testing.T) {
+		wallet := Wallet{}
+		wallet.Deposit(10)
+		assertBalance(t, wallet, Bitcoin(10))
+	})
+	t.Run("withdraw", func(t *testing.T) {
+		wallet := Wallet{balance: Bitcoin(20)}
+		wallet.Withdraw(10)
+		assertBalance(t, wallet, Bitcoin(10))
+	})
 }