Small Interfaces

Go interfaces usually work best when consumers define only the behavior they need.

small_interfaces.go

package main

import "fmt"

func main() {
	var methodCount = 
	interfaceName := "Reader"
	if methodCount > 1 {
		interfaceName = "Repository"
	}

	focused := methodCount <= 2
	testDouble := "simple fake"
	if !focused {
		testDouble = "large mock"
	}

	fmt.Println("interface=", interfaceName)
	fmt.Println("methods=", methodCount)
	fmt.Println("focused=", focused)
	fmt.Println("test_double=", testDouble)
}

package main

import "fmt"

func main() {
	var methodCount = 
	interfaceName := "Reader"
	if methodCount > 1 {
		interfaceName = "Repository"
	}

	focused := methodCount <= 2
	testDouble := "simple fake"
	if !focused {
		testDouble = "large mock"
	}

	fmt.Println("interface=", interfaceName)
	fmt.Println("methods=", methodCount)
	fmt.Println("focused=", focused)
	fmt.Println("test_double=", testDouble)
}

package main

import "fmt"

func main() {
	var methodCount = 
	interfaceName := "Reader"
	if methodCount > 1 {
		interfaceName = "Repository"
	}

	focused := methodCount <= 2
	testDouble := "simple fake"
	if !focused {
		testDouble = "large mock"
	}

	fmt.Println("interface=", interfaceName)
	fmt.Println("methods=", methodCount)
	fmt.Println("focused=", focused)
	fmt.Println("test_double=", testDouble)
}

interfaces Small consumer-owned interfaces keep packages decoupled and tests simple.