Environment file with Newman in Postman - Build an Automation Script

Run Postman collection with environment file using Newman

Preconditions (3)

Step 1: Open terminal or command prompt

Step 2: Run Newman command to execute the collection with the environment file: newman run <collection-file.json> -e <environment-file.json>

Step 3: Observe the test run output in the terminal

✅ Expected Result: Newman runs the collection using the environment variables from the environment file and shows the test results in the terminal

Automation Requirements - Newman CLI

Assertions Needed:

Verify that Newman command runs without errors

Verify that environment variables are correctly loaded and used in the requests

Verify that test assertions in the collection pass

Best Practices:

Use explicit environment file with -e option

Check exit code of Newman command for success

Use descriptive names for environment variables

Keep environment files secure and do not commit sensitive data

Automated Solution

Postman

import subprocess

# Define paths to collection and environment files
collection_file = 'MyCollection.json'
environment_file = 'MyEnvironment.json'

# Run Newman command with environment file
result = subprocess.run([
    'newman', 'run', collection_file,
    '-e', environment_file
], capture_output=True, text=True)

# Print Newman output
print(result.stdout)

# Assert that Newman run was successful
assert result.returncode == 0, f"Newman run failed with exit code {result.returncode}"

This script uses Python's subprocess module to run the Newman CLI command that executes a Postman collection with a specified environment file.

The newman run command includes the -e option to specify the environment file, ensuring environment variables are loaded.

The script captures the output and prints it, so you can see the test run results in the console.

Finally, it asserts that the Newman command exited with code 0, which means the run was successful.

This approach automates running the collection with environment variables and verifies the execution result.

Common Mistakes - 4 Pitfalls

Not specifying the environment file with the -e option

Hardcoding sensitive data directly in the collection or script

{'mistake': 'Ignoring the exit code of the Newman command', 'why_bad': "You may miss test failures or errors if you don't check the exit code.", 'correct_approach': 'Check the return code after running Newman to confirm success or failure.'}

Using relative paths without confirming current working directory

Bonus Challenge

Now add data-driven testing by running the same collection with three different environment files

Show Hint

Practice

1. What is the main purpose of an environment file in Postman when running tests with Newman?

easy

A. To store variables that customize test runs

B. To write test scripts

C. To save the test results

D. To create new API endpoints

Solution

1. Step 1: Understand environment file role

   Environment files hold variables like URLs or tokens to change test behavior without editing tests.

2. Step 2: Connect to Newman usage

   Newman uses these files to run the same tests with different settings easily.

3. Final Answer:

   To store variables that customize test runs -> Option A

4. Quick Check:

   Environment file = variables for tests [OK]

Hint: Environment files hold variables for flexible test runs [OK]

Common Mistakes:

• Confusing environment files with test scripts
• Thinking environment files save test results
• Assuming environment files create API endpoints

2. Which Newman command option is used to specify an environment file when running a collection?

easy

A. -c

B. -e

C. -d

D. -r

Solution

1. Step 1: Recall Newman command options

   Newman uses -e to load environment files, -c for collections, -d for data files, and -r for reporters.

2. Step 2: Identify correct option for environment file

   The correct option to specify environment file is -e.

3. Final Answer:

   -e -> Option B

4. Quick Check:

   Environment file option = -e [OK]

Hint: Use -e option to load environment files in Newman [OK]

Common Mistakes:

• Using -c instead of -e for environment files
• Confusing data file option -d with environment file
• Using -r which is for reporters

3. Given the Newman command:
newman run mycollection.json -e dev_environment.json
What will happen during this test run?

medium

A. Newman runs tests and saves results to dev_environment.json

B. Newman ignores the environment file and runs default variables

C. Newman runs tests but fails due to missing environment file

D. Newman runs tests using variables from dev_environment.json

Solution

1. Step 1: Analyze the command structure

   The command uses -e dev_environment.json which tells Newman to load that environment file.

2. Step 2: Understand effect on test run

   Newman will use variables from the specified environment file during the test run.

3. Final Answer:

   Newman runs tests using variables from dev_environment.json -> Option D

4. Quick Check:

   -e loads environment variables [OK]

Hint: -newman run ... -e loads environment variables [OK]

Common Mistakes:

• Assuming environment file is ignored
• Thinking results are saved to environment file
• Confusing environment file with data file

4. You run Newman with the command:
newman run collection.json -e wrong_env.json
but get an error saying the environment file is not found. What is the most likely cause?

medium

A. Newman does not support environment files

B. The collection file is missing variables

C. The environment file path or name is incorrect

D. The -e option is not valid in Newman

Solution

1. Step 1: Understand the error message

   Error says environment file not found, meaning Newman cannot locate the file.

2. Step 2: Identify common causes

   Most likely the file path or filename is wrong or file is missing.

3. Final Answer:

   The environment file path or name is incorrect -> Option C

4. Quick Check:

   File not found = wrong path/name [OK]

Hint: Check environment file path and name carefully [OK]

Common Mistakes:

• Assuming Newman does not support environment files
• Blaming collection file for environment file errors
• Using invalid Newman options

5. You want to run the same Postman collection with two different environment files: staging.json and production.json. How can you automate this using Newman in a single command or script?

hard

A. Run two separate Newman commands, each with its own -e option

B. Use one Newman command with both environment files listed after -e

C. Merge both environment files into one and use -e once

D. Newman cannot run multiple environments; run manually

Solution

1. Step 1: Understand Newman environment usage

   Newman accepts only one environment file per run with -e.

2. Step 2: Automate multiple runs

   To run with two environments, run Newman twice, each time specifying one environment file.

3. Final Answer:

   Run two separate Newman commands, each with its own -e option -> Option A

4. Quick Check:

   One environment per run; use multiple commands [OK]

Hint: Run Newman twice, each with one environment file [OK]

Common Mistakes:

• Trying to pass multiple environment files in one command
• Merging environment files incorrectly
• Assuming Newman supports multiple environments in one run