FileMaker Testing, Part 1 – Your First Test


With the release of FileMaker 16 and native JSON functions, the ability to create a testable solution has been vastly improved. In this blog post, I will walk you through a simple example of what testing is, and how it can improve your solutions. Most developers have had situations where they need to alter some existing logic, and are concerned that they might alter something with unforeseen consequences. Wouldn’t it be nice if you could ensure that your changes didn’t break existing code? Welcome to FileMaker Testing.

Automated Software Testing

Software testing has a lot of different variations and buzzwords associated with it. You’ll hear all sorts of phrases and acronyms thrown about like TDD, BDD, Unit Testing, Regression Testing, etc. It’s worth a learning a little something about these at some point. But at the heart of all of them is a simple concept; write some code to automatically test some other code.  If you do, your code will be less fragile, and easier to maintain.

What is FileMaker Testing?

A test is a FileMaker just script used to ensure that other scripts are working properly. Tests ensure that scripts are not only accomplishing their goal but also producing the desired result when they fail. While there are many ways to perform FileMaker testing, we test using the following assumptions:

  1. Each script to be tested accepts & returns JSON as a parameter
  2. We will be using custom functions for handling errors, testing JSON objects, and validating a JSON payload

Writing Testable Scripts

To prepare your script that needs to be tested, it should always return JSON to the script that called it. This means that if the script fails, it should return an error JSON object. If it succeeds, it should return an object representing the data that was changed. See the example script called “Create a Project” in FileToTest. You will notice that it returns verbose errors on all failures, and returns a JSON object when successful.

Writing The Test Script

To prepare your test script, you need to do three things in karbon_tester:

  1. Create a JSON Object to pass the script using the layout “Edit Test Data”
  2. Create a script in the Folder “Project Testing” (Copy the existing scripts…you’ll get the idea!)
  3. Add the script you created to the script “Test – Project”

Do We Test Every Script?

There is no reason to test each & every script. We only write tests for those scripts that play a critical role in the solution. Once you are comfortable with testing, it will become clear what you should test. It’s up to you.

Benefits of FileMaker Testing

The benefits of creating test scripts are compelling. First, it provides any solution with a level of stability that is difficult to achieve in a timely fashion. If multiple developers are collaborating on the same solution, the test file enables everyone to run common tests on core business logic, and see if they have produced any unforeseen fatal errors.

Second, it provides a level of clarity for you, the developer. Once you begin writing tests, you will take on an alternate persona, where you are actively poking holes in your own code. This may seem like a small difference, but we believe you’ll be surprised once you try it. You become much more critical, which improves your focus & clarity.

Third, the readability of your code will improve. One thing that makes JSON difficult to handle is that there is not a repository for JSON objects within a FileMaker solution. When a script is designed to handle records in multiple tables, karbon_tester serves as a clear, contextual example of how to create & pass JSON objects to work within a solution.

Is it Worth It?

The first question many people seem to ask when introduced to testing is “is this worth it?” Our answer would be that it depends on the solution. If you have a complex system, multiple developers, and a need for stable solutions, it’s not just worth it, it should be the standard.


To start, download our sample files here. Open “FileToTest”, and create a project. Review the script “Create a Project” to see how the file works. Then open the file “Karbon_Tester” and run the existing test. See how easy that was? Now you should create your own scripts to test creating a status.

What About Editing Data & Managing Test Data?

We will be releasing part 2 in this series in the future. We will walk through options for loading test data, & managing records that are used only for testing. The testing in this sample is intentionally simple to grasp and does not confront some of the nuanced issues involved in testing.

What about Karbon?

We know some have you have been waiting for us to release some of internal tools and frameworks that we group under something we call “Karbon”.  This is the piece piece of that puzzle.  More coming soon.

4 responses to “FileMaker Testing, Part 1 – Your First Test”

  1. Tom Horton says:


    The Error custom function in the FileToTest.fmp12 file has a in the code:

    Error ( errorCode ; descriptor ; data )
    Let (
    e = errorCode;
    e = If( IsEmpty ( e ) ; 0 ; GetAsNumber(e) );

    base = JSONSetElement ( “” ; “errorCode” ; e ; JSONNumber ) ;

    basePlusMessage = If ( e >= -1 ; JSONSetElement ( base ; “errorMessage”; (e) ; JSONString) ; base )
    ] ;

    not e ; base ;
    JSONSetElement( basePlusMessage ;
    [“scriptName” ; Get(ScriptName) ; JSONString];
    [“type” ; “FM” ; JSONString] ;
    [“descriptor” ; descriptor ; JSONString] ;
    [“data” ; data ; JSONObject]



    Is it just the copy I downloaded from github?

  2. Lance Brandenberg says:

    Hey Tom,

    I uploaded a new “FileToTest” on GitHub with the proper custom function. Thanks for the feedback!

    I’d like to point out that we do keep custom functions in their own repository so that they can be improved over time. If you ever have a problem with a custom function, you can always check what’s in your file against the repository.

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