Unit testing

Generally the developers tend to write the code which works only for valid user input or arguments and end up releasing the same for testing (no unit testing, no refactoring and no optimization).
C# example
Step #1 - Write the code for all possible invalid condition.

//should not allow empty string or null string
public bool SetName(string strName)
{
    bool blnStatus = false;
    if (strName != string.Empty && strName != null)
    {

    }
    return blnStatus;
}

Step #2 - Perform a quick unit test.

Example unit test cases.

• Test the code for empty string and expect the function to return false
• Test the code for null string and expect the function to return false
• If any of the above case fails fix the code without writing the code for invalid case
• When all the above cases succeed write the code for valid case

Step #3 - Fix the defects and verify the fixes if any.

C# example

Step #4 - Write the code for all valid conditions.

//should not allow empty string or null string
public bool SetName(string strName)
{
    bool blnStatus = false;
    if (strName != string.Empty && strName != null)
    {
        m_strName = strName;
        blnStatus = true;
    }
    return blnStatus;
}

Step #5 - Perform the unit test for the entire functionality.

Example unit test cases.

• Test the code for empty string and expect the function to return false
• Test the code for null string and expect the function to return false
• Next add the test case for valid string value and expect the function to return true
• If any of the above case fails fix the code and verify the same

Step #6 - Fix the defects and verify the fixes if any.

Write invalid condition code → Unit test → Fix & Verify → Write valid condition code → Unit test → Fix & Verify

Note: Unit testing automation strategy has to planned well before starting the implementation. There are unit testing automation frameworks available in the open source community as well as COTS.

Rule: Unit test the function.