GO_Learning_TDD_introduction

Definition

TDD is the abbreviation of Test Drive Development. In my view, that is a kind of develop procedure or develop concept. From the point of develop procedure, TDD can be divided into a circle:

• Write a test
• Make the complie pass
• Run the test, see that it fails and check the error message is meaningful
• Write enough code to make the test pass
• Refactor

The circle aboved can be called code flow. In long term, that will help developer.

Goodness

• Make sure code module is self-contained;
• Test first make sure you have a clear goal

Badness

• Tedious

Example

Hello World is a good start to understand TDD producre.

Write a Simple Test

Implement the simplest feature.

package main

import "testing"

func TestHello(t *testing.T) {
    got := Hello()
    want := "Hello, world"

    if got != want {
        t.Errorf("got %q want %q", got, want)
    }
}

Implement Simple Code Feature

package main

import "fmt"

func Hello() string {
    return "Hello, world"
}

func main() {
    fmt.Println(Hello())
}

Run The Test

This part we need to check some points :

• Write a failing test and see it fail so we know we have written a relevant test for our requirements and seen that it produces an easy to understand description of the failure
• Writing the smallest amount of code to make it pass so we know we have working software
• Then refactor, backed with the safety of our tests to ensure we have well-crafted code that is easy to work with

Enrich the test and go back to the first step;

More Complate Test

For Hello World , We want infer Some Name , not just “world”,like “Hello QingZhi”. So we chang the Test file, like this:

func TestHello(t *testing.T) {

    assertCorrectMessage := func(t testing.TB, got, want string) {
        t.Helper()
        if got != want {
            t.Errorf("got %q want %q", got, want)
        }
    }

    t.Run("saying hello to people", func(t *testing.T) {
        got := Hello("Chris")
        want := "Hello, Chris"
        assertCorrectMessage(t, got, want)
    })

    t.Run("empty string defaults to 'World'", func(t *testing.T) {
        got := Hello("")
        want := "Hello, World"
        assertCorrectMessage(t, got, want)
    })

}

More Complate Code

Not much word , just look at the feature code:

const englishHelloPrefix = "Hello, "

func Hello(name string) string {
    if name == "" {
        name = "World"
    }
    return englishHelloPrefix + name
}

Run the test again

Check the feature code is suitable with test goal. And Enrich feature again, like add other country language :Chinese “你好, QingZhi”.

Complate Test

package main

import "testing"

func TestHello(t *testing.T) {

	assertCorrectMessage := func(t testing.TB, got, want string) {
		t.Helper()
		if got != want {
			t.Errorf("got %q want %q", got, want)
		}
	}

	t.Run("to a person", func(t *testing.T) {
		got := Hello("Chris", "")
		want := "Hello, Chris"
		assertCorrectMessage(t, got, want)
	})

	t.Run("empty string", func(t *testing.T) {
		got := Hello("", "")
		want := "Hello, World"
		assertCorrectMessage(t, got, want)
	})

	t.Run("in Spanish", func(t *testing.T) {
		got := Hello("Elodie", spanish)
		want := "Hola, Elodie"
		assertCorrectMessage(t, got, want)
	})

	t.Run("in French", func(t *testing.T) {
		got := Hello("Lauren", french)
		want := "Bonjour, Lauren"
		assertCorrectMessage(t, got, want)
	})

}

Complate Code

package main

import "fmt"

const spanish = "Spanish"
const french = "French"
const englishHelloPrefix = "Hello, "
const spanishHelloPrefix = "Hola, "
const frenchHelloPrefix = "Bonjour, "

// Hello returns a personalised greeting in a given language.
func Hello(name string, language string) string {
	if name == "" {
		name = "World"
	}

	return greetingPrefix(language) + name
}

func greetingPrefix(language string) (prefix string) {
	switch language {
	case french:
		prefix = frenchHelloPrefix
	case spanish:
		prefix = spanishHelloPrefix
	default:
		prefix = englishHelloPrefix
	}
	return
}

func main() {
	fmt.Println(Hello("world", ""))
}

Run the Final Test

Final part , get the GREAT Hello World.