I Want to Test Local Plural Packages on Go

I faced the problem that it is difficult to test local plural packages on Go. For example, I want to test all packages (calculate and outLog) under src directory, as shown below.

./src
  |- calculate/
    |- calculate.go
    |- calculate_test.go
    |- go.mod
  |- outLog/
    |- outLog.go
    |- outLog_test.go
    |- go.mod
main.go
go.mod

You can test all packages using the below command if you do not make go.mod in calculate and outLog (it means that if you do not initialize calculate and outLog as a module).
However, you cannot use these packages on main.go if you do not initialize them as a module, so you should initialize them.

This article's goal is that I know how to test local plural packages after initializing them as packages(modules) on Go.
I could not find good TIPS in Google, so I took a trial-and-error. I want to share them.

On the other hand, Go has interface, so I guess that we can use DI(Dependency Injection) on Go. My guess is that it is better to test each local package after dividing dependencies among all packages(Single responsibility principle?), but I'm a beginner at using Go, so it is difficult for me to use DI for now. I shared this article topic as interim progress to DI.

Initialize Each Local Package (Module)

Before testing, I initialize each package using the following command.

go mod init [any name of your package you decided]
go mod tidy

After that, I make a path to each package. I run the following command on the directory, which has main.go.

go mod edit -replace [any name of your package you decided]=[relative path to each module]
go mod tidy

In this article, I named playground/calculate and playground/outLog to each package, so main.go has the following source code.

package main

import (
    "fmt"
    "playground/calculate"
    outlog "playground/outLog"
)

func main() {
    ol := outlog.OutLog{To_console: true, To_file: false}
    ol.Error("Success to output an Error🎉")
    res := calculate.Calculate(3)
    fmt.Printf("The result of calculation：%d", res)
}

How to Test All Packages?

Test Files on the Directory, Which Has main.go

I'm sure that I can test all packages if I make a test file on the directory, which has main.go as shown below.

package main

import (
    "playground/calculate"
    outlog "playground/outLog"
    "testing"
)

func TestCal(t *testing.T) {
    result := calculate.Calculate(2)
    if result != 2*2 {
        t.Fatal("Not match the result of calculation.")
    }
}

func TestConsole(t *testing.T) {
    outLog := outlog.OutLog{To_console: true, To_file: false}
    rec, err := outLog.Error("Please find me!!🐬")
    if rec == "" || err != nil {
        t.Fatal("The failed to output an error.")
    }
}

After that, I run the following command on the directory, which has main.go.

go test -v ./...

However, I do not want to test in this way because I have to make a lot of test files on the directory which has main.go.

Test All Packages using go test -v [package name]

This is a better solution, I think, but this command will be long if I use a log to packages.
In this article, go.mod of main.go is the following.

module playground/main

go 1.18

replace playground/outLog => ./src/outLog

replace playground/calculate => ./src/calculate

require (
    playground/calculate v0.0.0-00010101000000-000000000000
    playground/outLog v0.0.0-00010101000000-000000000000
)

I run the following command on the directory, which has main.go if I want to test playground/calculate and playground/outLog.

go test -v playground/calculate playground/outLog

After that command runs, I get the following result.

=== RUN   TestCal
--- PASS: TestCal (0.00s)
PASS
ok      playground/calculate    (cached)
=== RUN   TestConsole
2022/06/17 15:55:19 [2022-06-17T15:55:19+09:00][Error] - Please find me!!🐬
--- PASS: TestConsole (0.00s)
PASS
ok      playground/outLog   (cached)

In this way, the directory has main.go does not need to have too many test files. It is a good point.

Conclusion

I do not have the best idea to resolve this problem. If you have any good ideas to resolve it, I would greatly appreciate it if you could let me know your idea.

---

This original article is the following that is written by me. This is a translation of a portion of this original article from Japanese to English.

Goで一度に複数パッケージのテストをしたい

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