funcmock

MockFunc - Overview and Disclaimer

This is a wrapper around github.com/stretchr/testify package.

We keep the API as close as possible to the original package.

We only aim to cover the most common use cases of function mocking.

At the moment we support GoLang versions >= 1.22.

Installation

go get github.com/ktsivkov/funcmock

Usage

Using a concrete type

package example

import (
	"errors"
	"testing"

	"github.com/stretchr/testify/assert"

	"github.com/ktsivkov/funcmock"
)

type SimpleFunction func(string, string) (string, error)

type Service struct {
	simpleFunction SimpleFunction
}

func (s Service) Do() (string, error) {
	return s.simpleFunction("a", "b")
}

func TestService(t *testing.T) {
	expectedErr := errors.New("test")
	expectedOut := "a"

	fnBuilder := funcmock.For[SimpleFunction]()
	fnBuilder.On("a", "b").Return(expectedOut, expectedErr)
	defer fnBuilder.AssertNumberOfCalls(t, 1)
	defer fnBuilder.AssertExpectations(t)

	fn := fnBuilder.Build()
	service := Service{fn}

	res, err := service.Do()
	assert.ErrorIs(t, err, expectedErr)
	assert.Equal(t, expectedOut, res)
}

Using an assumed type

package example

import (
	"errors"
	"fmt"
	"testing"

	"github.com/stretchr/testify/assert"

	"github.com/ktsivkov/funcmock"
)

type SimpleFunction func(string, string) (string, error)

func MyFunction(a string, b string) (string, error) {
	return fmt.Sprintf("%s_%s", a, b), nil
}

type Service struct {
	simpleFunction SimpleFunction
}

func (s Service) Do() (string, error) {
	return s.simpleFunction("a", "b")
}

func TestService(t *testing.T) {
	expectedErr := errors.New("test")
	expectedOut := "a"

	fnBuilder := funcmock.As(MyFunction)
	fnBuilder.On("a", "b").Return(expectedOut, expectedErr)
	defer fnBuilder.AssertNumberOfCalls(t, 1)
	defer fnBuilder.AssertExpectations(t)

	fn := fnBuilder.Build()
	service := Service{fn}

	res, err := service.Do()
	assert.ErrorIs(t, err, expectedErr)
	assert.Equal(t, expectedOut, res)
}