main_test.go

package main

import "testing"

func TestDoubleMe(t *testing.T) {
	table := []struct {
		input    float64
		expected float64
	}{
		{1, 2},
		{-1, -2},
		{0, 0},
		{-100, -200},
		{100, 200},
	}

	for _, test := range table {
		result := doubleMe(test.input)
		if result != test.expected {
			t.Errorf("doubleMe(%f) = %f, expected %f", test.input, result, test.expected)
		}
	}
}