Test Driven Development
Why? How? Wow!
Jan Kolárik
Agenda
- Introduction
- Lifecycle
- Hands-on project
- Aiming for great code
- Conclusion
Motivation
Reshaping the conventional cycle
Motivation
But why would we do that?
Motivation
Build confidence and control
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Motivation
Gain a new perspective
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Motivation
Drive yourself to clean code
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Motivation
Take it as a game, challenge yourself
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Lifecycle
Designing a pub
Beer
🍺
Bill
📜
Client
Waiter
Beer, anyone? 🍺
Requirements:
- Drinkable (at once)
- Check it's full
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
interface IBeer
{
bool IsFull();
void Drink();
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
}
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
throw new NotImplementedException();
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
throw new NotImplementedException();
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
⬜ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
return true;
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
return true;
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
[Test]
public void BeerIsEmptyAfterDrinking() {
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
return true;
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
[Test]
public void BeerIsEmptyAfterDrinking() {
var beer = new Beer();
beer.Drink();
Assert.IsFalse( beer.IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
return true;
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
[Test]
public void BeerIsEmptyAfterDrinking() {
var beer = new Beer();
beer.Drink();
Assert.IsFalse( beer.IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
}
public bool IsFull() {
return true;
}
public void Drink() {
throw new NotImplementedException();
}
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
⬜ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
[Test]
public void BeerIsEmptyAfterDrinking() {
var beer = new Beer();
beer.Drink();
Assert.IsFalse( beer.IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
this.isFull = true;
}
public bool IsFull() {
return isFull;
}
public void Drink() {
isFull = false;
}
private bool isFull;
}
Beer, anyone? 🍺
Test list:
✅ New beer is full
✅ Drunk beer is empty
[TestFixture]
class BeerTest
{
[Test]
public void BeerIsFullAfterCreation() {
Assert.IsTrue( new Beer().IsFull() );
}
[Test]
public void BeerIsEmptyAfterDrinking() {
var beer = new Beer();
beer.Drink();
Assert.IsFalse( beer.IsFull() );
}
}
class Beer : IBeer
{
public Beer() {
this.isFull = true;
}
public bool IsFull() {
return isFull;
}
public void Drink() {
isFull = false;
}
private bool isFull;
}
Pay the bills 📜
Requirements:
- Track beers
- Pay
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
interface IBill
{
void AddBeer();
void Pay( uint count );
uint GetUnpaidCount();
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, new Bill().GetUnpaidCount() );
}
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
throw new NotImplementedException();
}
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
throw new NotImplementedException();
}
}
Pay the bills 📜
Test list:
⬜ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
throw new NotImplementedException();
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return 0;
}
}
Pay the bills 📜
Test list:
✅ New bill is empty
⬜ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
beers = beers + 1;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return beers;
}
private uint beers = 0;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
}
public void AddBeer() {
beers = beers + 1;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return beers;
}
private uint beers = 0;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
throw new NotImplementedException();
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
⬜ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
[Test]
public void PayTooManyThrowsAnException() {
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
[Test]
public void PayTooManyThrowsAnException() {
Assert.Catch( () => bill.Pay( 1 ) );
bill.AddBeer();
Assert.Catch( () => bill.Pay( 2 ) );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
[Test]
public void PayTooManyThrowsAnException() {
Assert.Catch( () => bill.Pay( 1 ) );
bill.AddBeer();
Assert.Catch( () => bill.Pay( 2 ) );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
⬜ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
[Test]
public void PayTooManyThrowsAnException() {
Assert.Catch( () => bill.Pay( 1 ) );
bill.AddBeer();
Assert.Catch( () => bill.Pay( 2 ) );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
if( count > unpaidBeers ) {
throw new Exception();
}
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Pay the bills 📜
Test list:
✅ New bill is empty
✅ Add beer
✅ Pay beer
✅ Pay too many
[TestFixture]
class BillTest
{
Bill bill;
[SetUp]
public void Init() {
bill = new Bill();
}
[Test]
public void GetUnpaidCountIsZeroByDefault() {
Assert.AreEqual( 0, bill.GetUnpaidCount() );
}
[Test]
public void AddBeerIncrementsUnpaidCount() {
bill.AddBeer();
Assert.AreEqual( 1, bill.GetUnpaidCount() );
bill.AddBeer();
Assert.AreEqual( 2, bill.GetUnpaidCount() );
}
[Test]
public void PayDecreasesUnpaidCount() {
bill.AddBeer();
bill.AddBeer();
bill.AddBeer();
bill.Pay( 2 );
Assert.AreEqual( 1, bill.GetUnpaidCount() );
}
[Test]
public void PayTooManyThrowsAnException() {
Assert.Catch( () => bill.Pay( 1 ) );
bill.AddBeer();
Assert.Catch( () => bill.Pay( 2 ) );
}
}
class Bill : IBill
{
public Bill() {
unpaidBeers = 0;
}
public void AddBeer() {
unpaidBeers++;
}
public void Pay( uint count ) {
if( count > unpaidBeers ) {
throw new Exception();
}
unpaidBeers -= count;
}
public uint GetUnpaidCount() {
return unpaidBeers;
}
private uint unpaidBeers;
}
Customer is always right
Requirements:
- Order beer
- Keep bill
- Pay bill
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
class Client : IClient
{
public Client() {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client() {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
}
public void OrderBeer() {
throw new NotImplementedException();
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
private IWaiter waiter;
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
this.waiter = waiter;
}
public void OrderBeer() {
waiter.Order( this );
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
private IWaiter waiter;
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
this.waiter = waiter;
}
public void OrderBeer() {
waiter.Order( this );
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
private IWaiter waiter;
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
this.waiter = waiter;
}
public void OrderBeer() {
waiter.Order( this );
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
private IWaiter waiter;
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
this.waiter = waiter;
}
public void OrderBeer() {
waiter.Order( this );
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
throw new NotImplementedException();
}
private IWaiter waiter;
}
Customer is always right
interface IClient
{
void OrderBeer();
void ReceiveBeer( IBeer beer );
void SetBill( IBill bill );
IBill GetBill();
void PayBill();
}
interface IWaiter
{
void Order( IClient client );
void Pay( IClient client );
}
class Client : IClient
{
public Client( IWaiter waiter ) {
this.waiter = waiter;
}
public void OrderBeer() {
waiter.Order( this );
}
public void SetBill( IBill bill ) {
throw new NotImplementedException();
}
public IBill GetBill() {
throw new NotImplementedException();
}
public void PayBill() {
throw new NotImplementedException();
}
public void ReceiveBeer( IBeer beer ) {
beer.Drink();
}
private IWaiter waiter;
}
Customer is always right
The rest is left as an exercise ...
Let's write great code
... by just using TDD?
SOLID code
Single responsibility
A module should be responsible to one, and only one, actor.
SOLID code
Single responsibility
SOLID code
Single responsibility
SOLID code
Open-closed principle
Entities should be open for extension, but closed for modification.
SOLID code
Open-closed principle
SOLID code
Open-closed principle
SOLID code
Liskov substitution
Subclasses should be interchangeable with their base classes seamlessly.
SOLID code
Liskov substitution
Apple apple = new Orange();
apple.GetColor();
SOLID code
Liskov substitution
Fruit fruit = new Orange();
fruit.GetColor();
SOLID code
Interface segregation
Clients should not be forced to depend on interfaces they do not use.
SOLID code
Interface segregation
interface ILaundry
{
void Wash();
void Dry();
}
class ComboWashingMashine : ILaundry
{
public void Wash() {
// do the work
}
public void Dry() {
// do the work
}
}
class SimpleWashingMashine : ILaundry
{
public void Wash() {
// do the work as well
}
public void Dry() {
// whoops, can't do
throw new NotImplementedException();
}
}
SOLID code
Interface segregation
interface IWashLaundry
{
void Wash();
}
interface IDryLaundry
{
void Dry();
}
class ComboWashingMashine : IWashLaundry,
IDryLaundry
{
public void Wash() {
// do the work
}
public void Dry() {
// do the work
}
}
class SimpleWashingMashine : IWashLaundry
{
public void Wash() {
// do the work
}
}
SOLID code
Dependency inversion
One should depend upon abstractions, not concretions.
SOLID code
Dependency inversion
SOLID code
Dependency inversion
Application
Device driver
Device driver
Device driver
- Simplified class diagram
- Business logic
- API parts
Device driver: Sending command
Device driver: Service intervention
Device driver: Reading values
Device driver: State change
Device driver: Summary
- Written in C++
- 3 projects: API, BL, Tests
- Complete BL coverage by TDD
- Almost 100 abstract classes
- More than 1300 test cases
Benefits
- Complete code coverage
- Living documentation
- Modular and extensible design
- Early bug detection
- Programmer confidence