Visual Basic for Applications:
Writing tests

How to:

While Visual Basic for Applications (VBA) doesn’t come with a built-in testing framework akin to those available in languages like Python or JavaScript, you can still implement simple test procedures to check the integrity of your code. Here’s an example to illustrate:

Suppose you have a function in VBA that adds two numbers:

Function AddNumbers(x As Integer, y As Integer) As Integer
    AddNumbers = x + y
End Function

To test this function, you can write another procedure that validates its output against expected results:

Sub TestAddNumbers()
    Dim result As Integer
    result = AddNumbers(5, 10)
    If result = 15 Then
        MsgBox "Test Passed!", vbInformation
    Else
        MsgBox "Test Failed. Expected 15 but got " & result, vbCritical
    End If
End Sub

Running TestAddNumbers will display a message box indicating whether the test passed or failed based on the function’s output. While this is a simplified scenario, you can build more complex tests by incorporating loops, different input values, and testing for multiple functions.

Deep Dive

The approach to writing tests in VBA shown here is manual and lacks the features of more sophisticated testing frameworks available in other programming environments, such as automated test runs, setup/teardown procedures, and integrated reporting of test results. Before the broader adoption of unit testing frameworks and test-driven development (TDD), manual testing procedures similar to the one described were common. While this method is simple and can be effective for small projects or learning purposes, it’s not scalable or efficient for larger projects or teams.

In environments that support richer development toolsets, programmers often turn to frameworks like NUnit for .NET applications or JUnit for Java applications, which provide comprehensive tools for writing and running tests systematically. These frameworks offer advanced features such as asserting test outcomes, setting up mock objects, and measuring code coverage.

For VBA developers looking for more advanced testing capabilities, the closest alternative might be leveraging external tools or integrating with other programming environments. Some developers use VBA in conjunction with Excel to record test scenarios and outcomes manually. While not as convenient or automated as using a dedicated testing framework, these methods can partially bridge the gap, helping maintain the reliability of VBA solutions in complex or critical applications.