Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Generating Random Testing Data.

Generating Random Testing Data

Written by Allen Wyatt (last updated January 13, 2024)
This tip applies to Excel 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021


1

When you develop worksheets that will be used by other people, you should test those worksheets to make sure that they work as you expect. This is particularly true of worksheets that contain complex formulas or will be used for critical purposes. The concept of testing a worksheet means that you will need to generate some sort of data to use in testing the worksheet.

Entire books have been written on putting together testing suites for software. How rigorous you are in compiling test data depends, in large part, on the needs of your audience and the nature of your worksheet. Unfortunately, there is no quick cure-all that will automatically figure out what you need and generate the data for you. There are tools in Excel, however, that you can use toward this end.

First, if you need to generate random numeric values, you can use the RAND or RANDBETWEEN worksheet functions. The difference is that RAND generates a value between 0 and 1, and RANDBETWEEN generates integer values between any bounds you set. Once you generate the values, then use copy and "paste values" to flatten your data to the results provided by the functions. (If you don't, then RAND and RANDBETWEEN will generate new results every time you recalculate the worksheet.)

Random data may not be appropriate for your testing needs, however. This is particularly true when you are testing boundaries of your formulas. For instance, testing with large values, small values, or a combination of large and small values. Likewise, you may want to test for inappropriate values, such as using text as input rather than numbers (or vice versa). There are a whole contingent of conditions you need to think through, and then pick the type of data that is right for your needs.

If you prefer, you can use macros to generate testing data. The following macro fills a selected range of cells with a random numeric value, between whatever boundaries (minimum and maximum) that you set.

Sub RandNums()
    Dim MyRange As Range
    Dim lMin As Long, lMax As Long
    Dim dRand As Double

    ' If selection is not Excel Range
    If TypeName(Selection) <> "Range" Then Exit Sub

    Set MyRange = Selection

    ' Get Min and Max value
    lMin = CLng(InputBox("Minimum?"))
    lMax = CLng(InputBox("Maximum?"))

    Randomize
    Application.ScreenUpdating = False

    For Each c In MyRange.Cells
        ' Calculate random value, where
        ' Value >= Min And Value <= Max
        dRand = Rnd * (lMax - lMin) + lMin

        ' Use the following line only if the random
        ' value should be an integer
        ' dRand = Int(dRand)

        c.Value = dRand
    Next c

    Application.ScreenUpdating = True
End Sub

To use the macro, just select a range of cells that you want to contain random numeric values, and then run the macro. If you must use integer values in the cells, then you can "uncomment" the noted line within the macro.

If you want to fill a range of cells with random dates, then a slight modification to the RandNums macro results in the following.

Sub RandDates()
    Dim MyRange As Range
    Dim dtMin As Date, dtMax As Date
    Dim dtRand As Date

    ' If selection is not Excel Range
    If TypeName(Selection) <> "Range" Then Exit Sub

    Set MyRange = Selection

    ' Get Min and Max value
    ' From: 1/1/1990 (put your start Date)
    dtMin = #1/1/1990#
    ' To: Today
    dtMax = Date

    Randomize
    Application.ScreenUpdating = False

    For Each c In MyRange.Cells
        ' Calculate random value, where
        ' Value >= Min And Value <= Max
        dtRand = Rnd * (dtMax - dtMin) + dtMin
        dtRand = Int(dtRand)

        c.Value = dtRand
        ' Change format for cell, below, as desired
        c.NumberFormat = "m/d/yyyy"
    Next c

    Application.ScreenUpdating = True
End Sub

Again, just select a range and then run the macro. You can modify the initial values set to the dtMin and dtMax variables in order to specify the boundaries for the dates desired. You can also, if desired, change the formatting applied to the cells after the random date is stored within the cells.

If you want to generate a group of names for testing purposes, then you are into the realm of textual values. A great way to do this is to simply do a search on the Web for the phrase "random name generator." There are a good number of websites available where you can generate names for free.

Note:

If you would like to know how to use the macros described on this page (or on any other page on the ExcelTips sites), I've prepared a special page that includes helpful information. Click here to open that special page in a new browser tab.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (7989) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021. You can find a version of this tip for the older menu interface of Excel here: Generating Random Testing Data.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company. ...

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What is 3 + 7?

2024-01-13 15:16:01

Dave Bonin

I always liked using a table of random numbers.

In particular, RAND Corp. published a table called 100,000 Random Normal Deviates (the title always makes me smile) in the 1950's. The table has been extensively tested and has no apparent statistical bias.

So why download and pick from a table of numbers?

1) Looking up random numbers (grab the next one in the table) is quick -- much quicker than generating random numbers.

2) Looking up random numbers (grab the next one in the table) is repeatable -- very important when you're trying to verify your formulas are correct.


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