How it works

The magic is mostly handled in the Pre-request script regarding checking an environment is selected. But what happens there allows to have more precise error message on 401 errors in Test script.

Collection Pre-request Script

Pre-request Script

/*******************************************/
/*  Checks a valid environment containing  */
/*  a specific variable used as bearer     */
/*  token is selected                      */
/*******************************************/

/* The name and default value of the variable used in Authorization
   and checked here is defined at collection level.
   That way, this code snippet can be easily copied to other
   collections */
const tokenVariableName = pm.collectionVariables.get("token_variable_name");
const tokenVariableDefaultValue = pm.collectionVariables.get("token_variable_default_value");
// The message indicating how to solve the problem
let message;
// Get selected environment name (undefined if none is selected)
const selectedEnvironment = pm.environment.name;
// Get token environment variable value (undefined if none exists or if current value is empty) 
const tokenVariableValue = pm.environment.get(tokenVariableName);

if(selectedEnvironment === undefined) {
    message = `No environment containing a ${tokenVariableName} variable has been selected`;
}
else if(tokenVariableValue === undefined) {
    message = `Selected environment (${selectedEnvironment}) does not contain a ${tokenVariableName} variable`;
}
else if(tokenVariableValue.length === 0) {
    message = `Selected environment (${selectedEnvironment}) contains a ${tokenVariableName} variable but its current value is empty`;
}
else if(tokenVariableValue === tokenVariableDefaultValue) {
    message = `Selected environment (${selectedEnvironment}) contains a ${tokenVariableName} variable but its current value is the default one (${tokenVariableDefaultValue})`;
}

if(message) {
    throw new Error(message);
}

The collection level Pre-Request script checks that an environment is selected by verifying the value of pm.environment.name .

It also checks a specific variable is defined and has a correct value. The name of that variable is defined in the token_variable_name collection variable. The script also verifies the the variable has a value and that value is not the default one.

If there’s anything wrong with one of the checks, the request is not sent and a red message explaining exactly what the problem is appears on screen thanks to throw new Error(message).

Collection Tests

Test Script

if(pm.response.code === 401) {
    const selectedEnvironment = pm.environment.name;
    const tokenVariableName = pm.collectionVariables.get("token_variable_name");
    const tokenVariableValue = pm.environment.get(tokenVariableName);
    const message = `Selected environment (${selectedEnvironment}) contains` +
                    `a ${tokenVariableName} variable but its value is` +
                    `probably not valid`;
    pm.test("Unauthorized request (401)", function() {
        pm.expect.fail(message);
    });
}

The collection level Tests script take for granted that the Pre-Request script has done its job. As there was an environment selected and it contains the expected variable which is not empty or does not have a default value, the test script can guess the token sent is invalid when receiving a 401 Unauthorized response.

Collection variables

In order to make the code easily reusable across various collection, some collection variable are used:

Environment variables

This collection requires the creation of an environment containing the following variables. This workspace comes with ready-to-use environment to test the various behaviors of the scripts (see Test cases below).

Test cases

Use one of the following test cases to see the collection level Pre-Script and Tests scripts in action.

No environment selected

1. Set environment drop list on “No Environment” (It’s the default value when opening the collection)
2. Send the Get a tweet request

Empty environment

1. Create an environment (don’t create any variable)
2. Select the environment
3. Send the Get a tweet request

Wrong name

1. Create an environment
2. Add a twitter_tokenn variable to your environment (yes, 2 n’s, it does not match the token_variable_name collection variable value)
3. Set INITIAL VALUE to PUT_YOUR_TOKEN_IN_CURRENT_VALUE (it matches token_variable_default_value collection variable value)
4. Save the environment
5. Select the environment
6. Send the Get a tweet request

Default value

1. Create an environment
2. Add a twitter_token variable to your environment (it matches the token_variable_name collection variable value)
3. Set INITIAL VALUE to PUT_YOUR_TOKEN_IN_CURRENT_VALUE (it matches token_variable_default_value collection variable value)
4. Save the environment
5. Select the environment
6. Send the Get a tweet request

Invalid token

1. Create an environment
2. Add a twitter_token variable to your environment (it matches the token_variable_name collection variable value)
3. Set INITIAL VALUE to PUT_YOUR_TOKEN_IN_CURRENT_VALUE (it matches token_variable_default_value collection variable value)
4. Set CURRENT VALUE to INVALID_TOKEN
5. Save the environment
6. Select the environment
7. Send the Get a tweet request

Valid token

1. Read Twitter API documentation to get a bearer token
2. Create an environment
3. Add a twitter_token variable to your environment (it matches the token_variable_name collection variable value)
4. Set INITIAL VALUE to PUT_YOUR_TOKEN_IN_CURRENT_VALUE (it matches token_variable_default_value collection variable value)
5. Put the bearer token value in twitter_token variable current value (NOT the initial value!)
6. Save the environment
7. Select the environment
8. Send the Get a tweet request