多国通貨(The Money Example) 三角測量(Equality for All)

テスト駆動開発
 楽天ブックス
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原著: Test Driven Development: By Example (Addison-Wesley Signature Series)

開発環境

テスト駆動開発 (Kent Beck(著)、和田卓人(翻訳)、オーム社)の第Ⅰ部(多国通貨(The Money Example))、第3章(三角測量(Equality for All))をJavaではなくGo言語で取り組んでみる。

コード

money_test.go

package money

import "testing"

func TestMultiplication(t *testing.T) {
	five := NewDollar(5)
	tests := []struct {
		m, want int
	}{
		{2, 10},
		{3, 15},
	}
	for _, test := range tests {
		got := five.Times(test.m).amount
		want := test.want
		if got != want {
			t.Errorf("five.Times(%v) got %v, want %v", test.m, got, want)
		}
	}
}

func TestEq(t *testing.T) {
	five := NewDollar(5)
	tests := []struct {
		d    Dollar
		want bool
	}{
		{NewDollar(5), true},
		{NewDollar(6), false},
	}
	for _, test := range tests {
		got := five.Eq(test.d)
		if got != test.want {
			t.Errorf("%v.Eq(%v) got %v, want %v",
				five, test.d, got, test.want)
		}
	}
}

money.go

package money

// Dollar ...
type Dollar struct {
	amount int
}

// NewDollar ...
func NewDollar(amount int) Dollar {
	return Dollar{amount: amount}
}

// Times ...
func (d Dollar) Times(m int) Dollar {
	return NewDollar(d.amount * m)
}

// Eq ...
func (d Dollar) Eq(c Dollar) bool {
	return d.amount == c.amount
}

入出力結果(Terminal, Zsh)

% go test
--- FAIL: TestEq (0.00s)
    money_test.go:34: {5}.Eq({6}) got true, want false
FAIL
exit status 1
FAIL	money	0.484s
% go test
PASS
ok  	money	0.229s
% go test
# money [money.test]
./money_test.go:14:28: five.Times(test.m).Amount undefined (type Dollar has no field or method Amount, but does have amount)
FAIL	money [build failed]
% go test
PASS
ok  	money	0.292s
%