Add app layer tests

app/convert_currency_test.go

@@ -0,0 +1,146 @@
+package app
+
+import (
+	"context"
+	"converter/app/mocks"
+	"converter/domain"
+	"converter/infrastructure/coinmarketcap"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+)
+
+func TestConvertCurrencyUseCase_Execute(t *testing.T) {
+	tests := []struct {
+		name      string
+		amount    string
+		fromCode  string
+		toCode    string
+		wantCode  string
+		wantErr   bool
+		setupMock func(*mocks.RateProvider)
+	}{
+		{
+			name:     "direct conversion - crypto to fiat",
+			amount:   "1.0",
+			fromCode: "BTC",
+			toCode:   "USD",
+			wantCode: "USD",
+			wantErr:  false,
+			setupMock: func(m *mocks.RateProvider) {
+				// Direct rate: BTC->USD
+				rateDTO := coinmarketcap.RateDTO{
+					FromCode: "BTC",     // Crypto symbol
+					ToCode:   "USD",     // Fiat code
+					FromName: "Bitcoin", // Crypto name from API
+					ToName:   "USD",     // Fiat code
+					Price:    50000.0,   // BTC price in USD
+					Source:   "coinmarketcap",
+				}
+				m.On("GetRate", mock.Anything, "BTC", "USD").Return(rateDTO, nil)
+			},
+		},
+		{
+			name:     "reversed conversion - fiat to crypto",
+			amount:   "50000.0",
+			fromCode: "USD",
+			toCode:   "BTC",
+			wantCode: "BTC",
+			wantErr:  false,
+			setupMock: func(m *mocks.RateProvider) {
+				// Reversed rate: requested USD->BTC but got BTC->USD
+				rateDTO := coinmarketcap.RateDTO{
+					FromCode: "BTC",     // What API actually returned
+					ToCode:   "USD",     // What API actually returned
+					FromName: "Bitcoin", // Crypto name from API
+					ToName:   "USD",     // Fiat code
+					Price:    50000.0,   // BTC price in USD (will be inverted)
+					Source:   "coinmarketcap",
+				}
+				m.On("GetRate", mock.Anything, "USD", "BTC").Return(rateDTO, nil)
+			},
+		},
+		{
+			name:     "invalid amount",
+			amount:   "invalid",
+			fromCode: "USD",
+			toCode:   "BTC",
+			wantCode: "",
+			wantErr:  true,
+			setupMock: func(m *mocks.RateProvider) {
+				// No mock setup needed - error occurs before calling provider
+			},
+		},
+		{
+			name:     "negative amount",
+			amount:   "-50.00",
+			fromCode: "USD",
+			toCode:   "BTC",
+			wantCode: "",
+			wantErr:  true,
+			setupMock: func(m *mocks.RateProvider) {
+				// No mock setup needed - error occurs before calling provider
+			},
+		},
+		{
+			name:     "rate not found",
+			amount:   "100.00",
+			fromCode: "XYZ",
+			toCode:   "ABC",
+			wantCode: "",
+			wantErr:  true,
+			setupMock: func(m *mocks.RateProvider) {
+				m.On("GetRate", mock.Anything, "XYZ", "ABC").Return(coinmarketcap.RateDTO{}, domain.ErrRateNotFound)
+			},
+		},
+		{
+			name:     "provider error",
+			amount:   "100.00",
+			fromCode: "USD",
+			toCode:   "INVALID",
+			wantCode: "",
+			wantErr:  true,
+			setupMock: func(m *mocks.RateProvider) {
+				m.On("GetRate", mock.Anything, "USD", "INVALID").Return(coinmarketcap.RateDTO{}, domain.ErrUnsupportedCurrency)
+			},
+		},
+		{
+			name:     "empty currency code",
+			amount:   "100.00",
+			fromCode: "",
+			toCode:   "BTC",
+			wantCode: "",
+			wantErr:  true,
+			setupMock: func(m *mocks.RateProvider) {
+				// No mock setup needed - error occurs before calling provider
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create fresh mock and use case for each test
+			mockProvider := mocks.NewRateProvider(t)
+			converter := domain.NewCurrencyConverter()
+			useCase := NewConvertCurrencyUseCase(mockProvider, converter)
+
+			// Setup mock expectations
+			tt.setupMock(mockProvider)
+
+			// Execute
+			result, err := useCase.Execute(context.Background(), tt.amount, tt.fromCode, tt.toCode)
+
+			// Assert error expectations
+			if tt.wantErr {
+				assert.Error(t, err, "Execute() should return error")
+				return
+			}
+
+			// Assert success case
+			assert.NoError(t, err, "Execute() should not return error")
+			assert.Equal(t, tt.wantCode, result.Currency.Code, "Currency code mismatch")
+			assert.True(t, result.Amount.IsPositive(), "Amount should be positive")
+		})
+	}
+}

app/mocks/RateProvider.go

@@ -0,0 +1,57 @@
+// Code generated by mockery v2.53.5. DO NOT EDIT.
+
+package mocks
+
+import (
+	context "context"
+	coinmarketcap "converter/infrastructure/coinmarketcap"
+
+	mock "github.com/stretchr/testify/mock"
+)
+
+// RateProvider is an autogenerated mock type for the RateProvider type
+type RateProvider struct {
+	mock.Mock
+}
+
+// GetRate provides a mock function with given fields: ctx, fromCode, toCode
+func (_m *RateProvider) GetRate(ctx context.Context, fromCode string, toCode string) (coinmarketcap.RateDTO, error) {
+	ret := _m.Called(ctx, fromCode, toCode)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetRate")
+	}
+
+	var r0 coinmarketcap.RateDTO
+	var r1 error
+	if rf, ok := ret.Get(0).(func(context.Context, string, string) (coinmarketcap.RateDTO, error)); ok {
+		return rf(ctx, fromCode, toCode)
+	}
+	if rf, ok := ret.Get(0).(func(context.Context, string, string) coinmarketcap.RateDTO); ok {
+		r0 = rf(ctx, fromCode, toCode)
+	} else {
+		r0 = ret.Get(0).(coinmarketcap.RateDTO)
+	}
+
+	if rf, ok := ret.Get(1).(func(context.Context, string, string) error); ok {
+		r1 = rf(ctx, fromCode, toCode)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// NewRateProvider creates a new instance of RateProvider. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
+// The first argument is typically a *testing.T value.
+func NewRateProvider(t interface {
+	mock.TestingT
+	Cleanup(func())
+}) *RateProvider {
+	mock := &RateProvider{}
+	mock.Mock.Test(t)
+
+	t.Cleanup(func() { mock.AssertExpectations(t) })
+
+	return mock
+}