Parameter override rules

This document explains the different override rules that occur when using parameters

There are various ways we can use parameters within to name a few we have - Data-Driven Testing, Groups, Exports Parameters, Configuration Files and Run Hooks and the Params file. Each override touches the test in different times, usually for different purposes. Let's review them.

The overriding Rules

Just like in most programming languages, where you define a variable, and the override is performed later, the variable comprises the last value assigned to it. Similarly, you can override a value in Testim.

Before the test begins:

Note: All parameters sent to a test have Local level visibility (the entire test though is considered to be a single big group).

During test run

The three visibility scopes are:

  • Local - the variables reside in a group, and are not accessible when the group is completed
  • Test - the variables reside in the test throughout the duration of the test.
  • Test Suite - the variables reside across multiple test executions and are passed from test to test.

Overriding rules

The more specific the visibility is, the higher its importance. If a variable is Local (most specific), it will always be used:

exports.x = "local"
exportsTest.x = "test"
exportsGlobal.x = "global"
console.log(x); // prints "local"


Data driven testing parameters:

Mostly used to create default set of values, which will be overridden by the config file or the hooks.

Note: you can provide a set of parameters (array of objects) and then run the same test several times.

Params file:
Similar to Data driven, but are not for a specific test. Those will be passed to all tests. E.g. common credentials

Config files:
Used to dynamically load a suite of parameters. You can run custom JS code, which is executed in node.js, thus giving you the ability to load and run any NPM package. Common cases are loading from DBs or CSV files. You can find code examples here.


  1. beforeTest and beforeSuite do NOT support returning a set of parameters (an array). If you pass an array, it will be treated as an object (i.e. in this context, return ["x", "y" "z"] is ALMOST equivalent to return {1: "x", 2: "y", ;3:"z"}).
  2. If you use the same parameters in both the beforeSuite and the overrideTestData, the beforeSuite value will be used

To override test data in beforeSuite, use the following format:

beforeSuite() {    
  return {
       y: 5,
       overrideTestData: {
           "testname1": [{x: 6}, {x:7}] , // runs testname1 twice
           "testname2": {y:7}          // y will be 5 because the beforeSuite object wins