如何在 Golang 中测试接口错误返回_Golang 错误注入与结果验证技巧

type UserRepository interface {
    GetUser(id int) (*User, error)
}

type MockUserRepo struct {
    err error
}

func (m *MockUserRepo) GetUser(id int) (*User, error) {
    return nil, m.err
}

repo := &MockUserRepo{err: errors.New("database timeout")}
service := NewUserService(repo)
user, err := service.GetUser(1)
if err == nil {
    t.Error("expected error, got nil")
}

if !errors.Is(err, ErrUserNotFound) {
    t.Errorf("want %v, got %v", ErrUserNotFound, err)
}

assert.ErrorIs(t, err, ErrUserNotFound)

tests := []struct {
    name    string
    repoErr error
    wantErr error
}{
    {"db_error", errors.New("connection failed"), ErrInternal},
    {"not_found", ErrUserNotFound, ErrUserNotFound},
}

for _, tt := range tests {
    t.Run(tt.name, func(t *testing.T) {
        repo := &MockUserRepo{err: tt.repoErr}
        service := NewUserService(repo)
        _, err := service.GetUser(1)
        if !errors.Is(err, tt.wantErr) {
            t.Errorf("want %v, got %v", tt.wantErr, err)
        }
    })
}

type Clock interface {
    Now() time.Time
}