Mock object pattern

workitemrepository.go

type WorkItemRepository struct {
	DoLoad   func(ctx context.Context, ID string) (*app.WorkItem, error)
	DoSave   func(ctx context.Context, wi app.WorkItem) (*app.WorkItem, error)
	DoDelete func(ctx context.Context, ID string) error
	DoCreate func(ctx context.Context, typeID string, fields map[string]interface{}) (*app.WorkItem, error)
	DoList   func(ctx context.Context, criteria criteria.Expression, start *int, length *int) ([]*app.WorkItem, uint64, error)
}

func (r *WorkItemRepository) Load(ctx context.Context, ID string) (*app.WorkItem, error) {
	return r.DoLoad(ctx, ID)
}
func (r *WorkItemRepository) Save(ctx context.Context, wi app.WorkItem) (*app.WorkItem, error) {
	return r.DoSave(ctx, wi)
}
func (r *WorkItemRepository) Delete(ctx context.Context, ID string) error {
	return r.DoDelete(ctx, ID)
}
func (r *WorkItemRepository) Create(ctx context.Context, typeID string, fields map[string]interface{}) (*app.WorkItem, error) {
	return r.DoCreate(ctx, typeID, fields)
}
func (r *WorkItemRepository) List(ctx context.Context, criteria criteria.Expression, start *int, length *int) ([]*app.WorkItem, uint64, error) {
	return r.DoList(ctx, criteria, start, length)
}

func testFunc() {
	var repo models.WorkItemRepository = &WorkItemRepository{
		DoList: func(ctx context.Context, criteria criteria.Expression, start *int, length *int) ([]*app.WorkItem, uint64, error) {
			return []*app.WorkItem{}, 0, nil
		},
	}
    ts:= ...
    service:= ...
	newcontroller := NewWorkitemController(service, repo, ts)
}

Mock base implementation has a func field for each interface function. Member functions call the corresponding func field