How to unit test custom types in Golang?

It is crucial to unit test custom types in Golang. Methods include: 1. Using the testing package: creating a Test function and reporting errors using t.Error(); 2. Using Mocking frameworks (such as gomock and mockery) : Create a mock type for testing; 3. Use an auxiliary function: Create an auxiliary function to test the type and use it in unit testing.

How to unit test custom types in Golang

Unit testing custom types is crucial because It ensures that the type behaves as expected. There are several ways to unit test custom types in Golang.

1. Use the standard testing package

testing package provides tools for writing and running unit tests. For custom types, you can use the Test function to define test cases and the t.Error() function to report errors:

package mypackage

import "testing"

type MyType struct {
    value int
}

func TestSum(t *testing.T) {
    myType := MyType{1}
    if myType.Sum(2) != 3 {
        t.Error("Expected 3, got", myType.Sum(2))
    }
}

2. Use Mocking Framework

The Mocking framework allows you to create custom types of mocks to test your code more easily. Popular Mocking frameworks include gomock and mockery:

Using gomock:

package mypackage

import (
    "testing"
    "github.com/golang/mock/gomock"
)

type MyInterface interface {
    DoSomething(value int)
}

func TestMyFunction(t *testing.T) {
    ctrl := gomock.NewController(t)
    defer ctrl.Finish()

    mockMyInterface := gomock.NewMockFrom(ctrl, "MyInterface")
    mockMyInterface.EXPECT().DoSomething(1).Return(nil)

    myFunction(mockMyInterface)
}

3. Using Auxiliary Function

Create a helper function to test your custom types, which can help you keep your code clean. You can then use this helper function in your unit tests:

package mypackage

import (
    "testing"
)

type MyType struct {
    value int
}

func TestSum(t *testing.T) {
    myType := MyType{1}
    if assertEqual(myType.Sum(2), 3, t) {
        t.Error("Expected 3, got", myType.Sum(2))
    }
}

func assertEqual(actual, expected int, t *testing.T) bool {
    if actual != expected {
        t.Errorf("Expected %d, got %d", expected, actual)
    }
    return actual == expected
}

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