Part 7: Source Code for a TDD Telephone Directory in Golang

Here is an example of a simple telephone directory implemented in Go using Test-Driven Development (TDD) principles:

package main

import (
    "fmt"
    "strings"
)

type Directory struct {
    contacts map[string]string
}

func (d *Directory) AddContact(name, phoneNumber string) {
    d.contacts[name] = phoneNumber
}

func (d *Directory) RemoveContact(name string) {
    delete(d.contacts, name)
}

func (d *Directory) UpdateContact(name, phoneNumber string) {
    d.contacts[name] = phoneNumber
}

func (d *Directory) FindContact(name string) (string, bool) {
    phoneNumber, ok := d.contacts[name]
    return phoneNumber, ok
}

func (d *Directory) FindContacts(query string) []string {
    var results []string
    for name, phoneNumber := range d.contacts {
        if strings.Contains(strings.ToLower(name), strings.ToLower(query)) {
            results = append(results, fmt.Sprintf("%s: %s", name, phoneNumber))
        }
    }
    return results
}

func main() {
    // Test the Directory using TDD principles
    d := &Directory{
        contacts: make(map[string]string),
    }
    d.AddContact("Alice", "123-456-7890")
    d.AddContact("Bob", "234-567-8901")
    d.AddContact("Eve", "345-678-9012")

    if phoneNumber, ok := d.FindContact("Alice"); !ok || phoneNumber != "123-456-7890" {
        fmt.Println("Error: Alice's phone number not found or incorrect")
    }
    if phoneNumber, ok := d.FindContact("Charlie"); ok {
        fmt.Println("Error: Charlie should not be in the directory")
    }

    d.UpdateContact("Bob", "333-333-3333")
    if phoneNumber, ok := d.FindContact("Bob"); !ok || phoneNumber != "333-333-3333" {
        fmt.Println("Error: Bob's phone number not updated correctly")
    }

    d.RemoveContact("Eve")
    if _, ok := d.FindContact("Eve"); ok {
        fmt.Println("Error: Eve should have been removed from the directory")
    }

    results := d.FindContacts("b")
    if len(results) != 1 || results[0] != "Bob: 333-333-3333" {
        fmt.Println("Error: FindContacts not working correctly")
    }

    fmt.Println("All tests pass.")
}

This code defines a Directory struct that has a contacts map field to store the name-phone number pairs. It also defines several methods to add, remove, update, and find contacts in the directory. Finally, it has a main function that tests these methods using TDD principles.

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