Add service test

domain/services_test.go

@@ -0,0 +1,71 @@
+package domain
+
+import (
+	"testing"
+
+	"github.com/shopspring/decimal"
+)
+
+func TestCurrencyConverter_Convert(t *testing.T) {
+	converter := NewCurrencyConverter()
+
+	usd, _ := NewCurrency("USD", "US Dollar", 2)
+	btc, _ := NewCurrency("BTC", "Bitcoin", 8)
+	eur, _ := NewCurrency("EUR", "Euro", 2)
+
+	tests := []struct {
+		name      string
+		money     Money
+		rate      Rate
+		wantErr   bool
+		wantCode  string
+	}{
+		{
+			name: "successful conversion",
+			money: func() Money {
+				m, _ := NewMoney("100", usd)
+				return m
+			}(),
+			rate: func() Rate {
+				r, _ := NewRate(usd, btc, decimal.NewFromFloat(0.00002), "test")
+				return r
+			}(),
+			wantErr:  false,
+			wantCode: "BTC",
+		},
+		{
+			name: "currency mismatch",
+			money: func() Money {
+				m, _ := NewMoney("100", eur)
+				return m
+			}(),
+			rate: func() Rate {
+				r, _ := NewRate(usd, btc, decimal.NewFromFloat(0.00002), "test")
+				return r
+			}(),
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := converter.Convert(tt.money, tt.rate)
+
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("Convert() expected error but got none")
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("Convert() unexpected error: %v", err)
+				return
+			}
+
+			if result.Currency.Code != tt.wantCode {
+				t.Errorf("Convert() currency = %s, want %s", result.Currency.Code, tt.wantCode)
+			}
+		})
+	}
+}