Unit test and State-based testing @ David Ko的學習之旅

Unit test and State-based testing

Source: The art of unit testing with examples in .NET, Roy Osherove
http://www.amazon.com/Art-Unit-Testing-Examples-Net/dp/1933988274/ref=sr_1_1?ie=UTF8&s=books&qid=1267086529&sr=1-1
Chapter 2 A first unit test

1. 簡單的單元測試範例
(1) 受測類別
先寫好程式, 等待之後測試
public class SimpleParser {
public int ParseAndSum( string numbers) {
    if (numbers.Length == 0)
      return 0;
    if ( !numbers.Contains(",") ) {
      return int.Parse(numbers);
    }
    else {
      throw new InvalidOperationException( "I can only handle 0 or 1 numbers for now!");
    }
}
}

(2) 測試程式
calss SimpleParserTests {
public static void TestReturnsZeroWhenEmptyString() {
    try {
      SimpleParser p = new SimpleParser();
      int result = p.ParseAndSum(string.Empty);
      if (result != 0) {
        Console.WriteLine("Parse and sum should have returned 0 on an empty string!");
      }
    }
    catch ( Exception e) {
      Console.WriteLine(e);
    }
}
}

(3)用console mode來驅動測試
public static void Main(string[] args) {
try {
SimpleParserTests.TestReturnsZeroWhenEmptyString();
}
catch( Exception e ) {
Console.WriteLine(e);
}
}

2. State-based testing
(1) 又稱state verification
(2) determine whether the exercised method worked correctly by examining the state of the system under test and its collaborators(dependencies) after the method is exercised
==> 所以重點在檢查受測程式和相關者的狀態是否正確
(3) 範例:

public class Log Analyzer {
private bool wasLastFileNameValid;

pubic bool WasLastFileNameValid {
    get { return wasLastFileNameValid; }
    set { wasLastFileNameValid = value; }
}

public bool IsValudLogFileName( string fileName ) {
    if ( !fileName.ToLower().EndsWith(".slf") ) {
      wasLastFileNameValid = false;
      return false;
    }

    // save state of result for later assertions
    wasLastFileNameValid = true;
    return true;
}
}

[Test]
public void IsValidLogFileName_ValidName_RemembersTrue() {
LogAnalyzer log = LogAnalyzer();
log.IsValidLogFileName("somefile.slf");
// 藉由檢查受測類別的狀態來確認測試是否成功
// 而不是檢查受測函式的傳回值
Assert.IsTrue(log.WasLastFileNameValid);
}