How to Change Functions to be Testable

Functions may need to be changed or written differently. It's easy to convert an example on a blog post about writing testable code for VoltScript. Imagine the following function:

Function getTimeOfDay() as String

    Dim nowTime as Variant
    nowTime = Now()
    If (Hour(Now) < 8) Then
        getTimeOfDay = "Night"
    ElseIf (Hour(Now) < 12) Then
        getTimeOfDay = "Morning"
    ElseIf (Hour(Now) < 6) Then
        getTimeOfDay = "Afternoon"
    Else
        getTimeOfDay = "Night"
    End If

End Function

This function is untestable, unless you are willing to test at multiple times of day or change the system time. Rewriting the function slightly can make it eminently testable:

Function getTimeOfDay(nowTime as Variant) as String

    If (Hour(Now) < 8) Then
        getTimeOfDay = "Night"
    ElseIf (Hour(Now) < 12) Then
        getTimeOfDay = "Morning"
    ElseIf (Hour(Now) < 6) Then
        getTimeOfDay = "Afternoon"
    Else
        getTimeOfDay = "Night"
    End If

End Function

Now it can be tested easily:

Dim testSuite as New TestSuite("Testing time of day")
Dim nowTime as Variant
nowTime = TimeNumber(4,30,04)  ' Fine because we're only interested in the time
Call testSuite.describe("Test Night am").assertEqualsString("Night", getTimeOfDay(nowTime), True)
nowTime = TimeNumber(8,30,04)
Call testSuite.describe("Test Morning").assertEqualsString("Morning", getTimeOfDay(nowTime), True)
nowTime = TimeNumber(13,30,04)
Call testSuite.describe("Test Afternoon").assertEqualsString("Afternoon", getTimeOfDay(nowTime), True)
nowTime = TimeNumber(20,30,04)
Call testSuite.describe("Test Night pm").assertEqualsString("Night", getTimeOfDay(nowTime), True)