feat(#17): CRUD de categorias — API Go + tela Vue + testes unitários

API REST /api/categories (GET/POST/PUT/DELETE) com regras de negócio:
categorias padrão não podem ser excluídas; categorias com transações vinculadas
também bloqueadas. Tela Vue com formulário inline de criação/edição, indicador
visual de categorias padrão e botão de exclusão condicional.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

apps/api/internal/service/category_test.go

@@ -0,0 +1,131 @@
+package service_test
+
+import (
+	"context"
+	"testing"
+
+	"financeiro-carvalho/internal/model"
+	"financeiro-carvalho/internal/repository"
+	"financeiro-carvalho/internal/service"
+)
+
+// mockCategoryRepo implements repository.CategoryRepository in memory.
+type mockCategoryRepo struct {
+	categories   []model.Category
+	txCount      map[int]int // category_id → transaction count
+}
+
+func newMockRepo(cats []model.Category) *mockCategoryRepo {
+	return &mockCategoryRepo{categories: cats, txCount: map[int]int{}}
+}
+
+func (m *mockCategoryRepo) List(_ context.Context) ([]model.Category, error) {
+	return m.categories, nil
+}
+
+func (m *mockCategoryRepo) GetByID(_ context.Context, id int) (*model.Category, error) {
+	for _, c := range m.categories {
+		if c.ID == id {
+			cp := c
+			return &cp, nil
+		}
+	}
+	return nil, repository.ErrNotFound
+}
+
+func (m *mockCategoryRepo) Create(_ context.Context, name, color string) (*model.Category, error) {
+	c := model.Category{ID: len(m.categories) + 1, Name: name, Color: color}
+	m.categories = append(m.categories, c)
+	return &c, nil
+}
+
+func (m *mockCategoryRepo) Update(_ context.Context, id int, name, color string) (*model.Category, error) {
+	for i, c := range m.categories {
+		if c.ID == id {
+			m.categories[i].Name = name
+			m.categories[i].Color = color
+			cp := m.categories[i]
+			return &cp, nil
+		}
+	}
+	return nil, repository.ErrNotFound
+}
+
+func (m *mockCategoryRepo) Delete(_ context.Context, id int) error {
+	for i, c := range m.categories {
+		if c.ID == id {
+			m.categories = append(m.categories[:i], m.categories[i+1:]...)
+			return nil
+		}
+	}
+	return repository.ErrNotFound
+}
+
+func (m *mockCategoryRepo) HasTransactions(_ context.Context, id int) (bool, error) {
+	return m.txCount[id] > 0, nil
+}
+
+// ── tests ──────────────────────────────────────────────────────────────────────
+
+func TestDeleteDefaultCategory_Rejected(t *testing.T) {
+	repo := newMockRepo([]model.Category{
+		{ID: 1, Name: "Saúde", Color: "#EF4444", IsDefault: true},
+	})
+	svc := service.NewCategoryService(repo)
+
+	err := svc.Delete(context.Background(), 1)
+	if err != service.ErrDefaultCategory {
+		t.Fatalf("expected ErrDefaultCategory, got %v", err)
+	}
+}
+
+func TestDeleteCategoryWithTransactions_Rejected(t *testing.T) {
+	repo := newMockRepo([]model.Category{
+		{ID: 2, Name: "Lazer", Color: "#10B981", IsDefault: false},
+	})
+	repo.txCount[2] = 3
+	svc := service.NewCategoryService(repo)
+
+	err := svc.Delete(context.Background(), 2)
+	if err != service.ErrHasTransactions {
+		t.Fatalf("expected ErrHasTransactions, got %v", err)
+	}
+}
+
+func TestDeleteUserCategory_OK(t *testing.T) {
+	repo := newMockRepo([]model.Category{
+		{ID: 3, Name: "Minha Cat", Color: "#123456", IsDefault: false},
+	})
+	svc := service.NewCategoryService(repo)
+
+	if err := svc.Delete(context.Background(), 3); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateCategory_EmptyName_Rejected(t *testing.T) {
+	svc := service.NewCategoryService(newMockRepo(nil))
+	_, err := svc.Create(context.Background(), model.CategoryInput{Name: "  ", Color: "#123456"})
+	if err != service.ErrEmptyName {
+		t.Fatalf("expected ErrEmptyName, got %v", err)
+	}
+}
+
+func TestCreateCategory_InvalidColor_Rejected(t *testing.T) {
+	svc := service.NewCategoryService(newMockRepo(nil))
+	_, err := svc.Create(context.Background(), model.CategoryInput{Name: "X", Color: "red"})
+	if err != service.ErrInvalidColor {
+		t.Fatalf("expected ErrInvalidColor, got %v", err)
+	}
+}
+
+func TestCreateCategory_OK(t *testing.T) {
+	svc := service.NewCategoryService(newMockRepo(nil))
+	cat, err := svc.Create(context.Background(), model.CategoryInput{Name: "Nova", Color: "#AABBCC"})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if cat.Name != "Nova" || cat.Color != "#AABBCC" {
+		t.Fatalf("unexpected result: %+v", cat)
+	}
+}