Go - bundles of code - Packages - Creating a new package, Importing package into a program, directories

Head First Go
楽天ブックス 紀伊國屋書店

開発環境

• macOS Mojave - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Go (プログラミング言語)

Head First Go (Jay McGavren(著)、O'Reilly Media)のChapter 4(bundles of code - Packages)、Pool Puzzle(122)の解答を求めてみる。

コード

~/go/src/calc/calc.go

package calc

func Add(first float64, second float64) float64 {
 return first + second
}
func Subtract(first float64, second float64) float64 {
 return first - second
}

sample1_test.go

package main

import (
 "calc"
 "testing"
)

func TestAdd(t *testing.T) {
 want := 3.0
 got := calc.Add(1, 2)
 if got != want {
  t.Errorf("Add(1, 2) = %v, want %v", got, want)
 }
}
func TestSub(t *testing.T) {
 want := 4.0
 got := calc.Subtract(7, 3)
 if got != want {
  t.Errorf("Subtract(7, 3) = %v, want %v", got, want)
 }
}

sample1.go

package main

func main() {}

入出力結果(Bash、cmd.exe(コマンドプロンプト)、Terminal)

$ go test
# _/.../go/Head_First_Go/ch4/sample1
sample1_test.go:4:2: cannot find package "calc" in any of:
 /.../go/src/calc (from $GOROOT)
 /.../go/src/calc (from $GOPATH)
FAIL _/.../go/Head_First_Go/ch4/sample1 [setup failed]
$ go test
# _/.../go/Head_First_Go/ch4/sample1 [_/.../go/Head_First_Go/ch4/sample1.test]
./sample1_test.go:11:9: invalid operation: got != want (mismatched types float64 and int)
./sample1_test.go:18:9: invalid operation: got != want (mismatched types float64 and int)
FAIL _/.../go/Head_First_Go/ch4/sample1 [build failed]
$ go test
PASS
ok   _/.../go/Head_First_Go/ch4/sample1 0.004s
$