Using xUnit as a Swiss-Aarmy Testing Toolkit

Using xUnit as a Swiss-Army Testing Toolkit
(Does ‘Unit’ Size Matter?)
ACCU Conference 2011
Chris Oldwood
gort@cix.co.uk

Stream of Consciousness
• Developer Driven Testing
• The Essence of (x)Unit Testing
• Those Pesky Dependencies
• Code & Test Evolution in Practice

Text Book Test
string[][] tests =
{
{ "3", "4", "+", "7" },
{ "9", "1", "-", "8" },
{ "2", "3", "*", "6" },
{ "9", "3", "/", "3" },
};
void run_tests()
{
var calculator = new Calculator();
foreach(var test in tests)
{
var lhs = test[0];
var rhs = test[1];
var op = test[2];
var result = calculator(lhs, rhs, op);
assert(result == test[3]);
}
}

Exercise Left for the Reader
External System 1 External System 2 External System 3
The System
42
ServicesDatabase

Unit
Integration
System Component
Stress
Lexicon of Testing
End-to-End
Regression
White Box
Black Box
Characterisation
Exploration

System
Integration
Component
Unit
Dependencies
Feedback
‘Unit’ Evolution
All Regression

Test == Specification
public void Execute_Should_Elide_Agreement_When_No_Trades_Match()
{
var trades = new List<Trade> { new Trade("trade-id", "product-a") };
var agreement = new Agreement("product-b");
var task = new PreparationTask(trades, agreement);
var result = task.Execute(s_services);
Assert.That(task.Agreement, Is.Null);
}

Consistent Style
public void a_c_sharp_test()
{
var arrangement = new Arrangement();
var result = arrangement.action();
Assert.That(result, Is.EqualTo(expectation));
}
create procedure a_sql_test
as
declare arrangement varchar(100),
result varchar(100)
exec action @input = arrangement,
@output = result
exec AssertAreEqual @result, "expectation"
go

Minimises Dependencies
MyService
External Service DatabaseFile System
Mock External
Service
IExternalService IFileSystem IDatabase
Mock File
System
Mock Database

Promotes Arbitrary Code Execution
public void Prepare_Should_Elide_Agreement_When_No_Trades_Match()
{
var trades = new List<Trade> { new Trade("trade-id", "product-a") };
var agreement = new Agreement("product-b");
var task = new PreparationTask(trades, agreement);
var result = task.Execute(s_services);
Assert.That(task.Agreement, Is.Null);
}
LibraryEXE Stub
Test Runner LibraryTestsDebugger
Custom Test
Harness

Automated Testing
• Lowers the barrier to running tests
• Regression testing is implicit
• Build server watches your back

Pesky Dependencies
External System 1 External System 2 External System 3
The System
Service 2
Service 1
File-System
Database

xUnit Abuse
• Fight the Shadow Cache
• Invoke TearDown from SetUp
• Test/build failure isn’t absolute

File-System (Reading)
• Source Control directory
• Build server directory
• Resource files

File-System (Writing)
• TEMP directory
• Output directory

Database
• Per-user / per-branch workspace
• Only need schema not data (Integration)
• Can reuse existing unit test database
• Use same code revision for compatibility
• Use transactions to avoid residual effects
• Fake tables with CSV files

Database Asserts
public void AddCustomer_Should_Persist_The_Customer()
{
const id = 1234;
const name = "name";
var customer = new Customer(. . .);
using (var connection = AcquireConnection())
{
CustomerDataMapper.AddCustomer(customer, connection);
Assert.That(RowExists("dbo.Customer",
" CustomerId = {0}"
+ " AND CustomerName = '{1}'",
id, name),
Is.True);
}
}

Database SetUp/TearDown
[TestFixture, TestCategory.DatabaseTest]
public class SomeEntityTests : DatabaseTestBase
{
[TestFixtureSetUp]
public void FixtureSetUp
{
using(var connection = AcquireConnection())
{
connection.Execute("insert into thingy_table values(1, 2, 3)");
connection.Execute("test.InsertThingy(1, 2, 3)");
}
}
[TestFixtureTearDown]
public void FixtureTearDown
{
using(var connection = AcquireConnection())
{
connection.Execute("delete from thingy_table");
connection.Execute("test.DeleteAllThingys");
}
}
}

Helper Base Class
public class DatabaseTestBase
{
public ISqlConnection AcquireConnection()
{
return . . .
}
. . .
public bool RowExists(string table, string where, string params[])
{
string filter = String.Format(where, params);
string sql = String.Format(
"select count(*) as [Count] from {0} where {1}"
, table, filter);
using (var connection = AcquireConnection())
{
var reader = connection.ExecuteQuery(sql);
return (reader.GetInt("Count") == 1);
}
}
. . .
}

External Systems
• Verify API behaviour
• Test internal façade
• Reliability varies (DEV vs PROD)

System Architecture
Market Data Trade Data Analytics
The System
42
ServicesDatabase

Initial System Test
Market
Data Service
Trade
Data Service
Analytics Service
Calculator
Test Runner
System Tests
[Test, TestCategory.SystemTest]
public void Calculate_Answer()
{
. . .
var result = c.calculate();
Assert.Equal(result, 42);
}

Addressing External Risks
External Market
Data Service API
External Trade
Data Service API
External Market
Data Service Tests
External Trade
Data Service Tests
Test Runner

Internal Service Design
External Service
API
External Service
Tests
Internal Service
External
Service Facade
Internal Service
Tests
Mock
External Services
Performance
Test Runner
Mock Service

Data Access Layer
Database
Public Interface
Database Unit
Tests
Data Access
Layer
Data Access
Layer Tests
Database API
Mock Database
API
Mock Data
Access Layer

Database
Public Interface
External Analytics
Service
External Market
Data Service API
External Market
Data Service API
System Evolution
Mock Market
Data Service
Mock Trade
Data Service
Mock Analytics
Service
Calculator
Test Runner
Unit / Integration
/ System Tests
[Test, TestCategory.SystemTest]
public void Calc_Answer_For_ABC_Plc()
{
. . .
var result = c.calculate();
Assert.Equal(result, 41.75);
}
Mock Data
Access Layer
Market
Data Service
Trade
Data Service
Analytics Service
Data Access
Layer

“The Oldwood Thing”
http://chrisoldwood.blogspot.com
Chris Oldwood
gort@cix.co.uk

Using xUnit as a Swiss-Aarmy Testing Toolkit

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