Testing APIs

Testing API’s using Postman

• Postman is a powerful HTTP client for testing web services. Postman makes it easy to test, develop and document APIs by allowing users to quickly put together both simple and complex HTTP requests.
• Postman with features required for API testing is available as free download and can be installed from https://www.getpostman.com/apps
• Postman can be used to perform Manual Testing, tests can also be automated with postman features of collections, Newman and with some scripting.

Manual Testing

• A simple GET request with no input/query parameters can be executed by providing the URL in postman window as GET request and Bearer token for authorization as in the below pic

Manual Testing – with Parameters

• A GET request with input/query parameters can be executed by providing the input parameter in URL of postman window as GET request. In the pic below term=Fall is passed as input to the API.
• The other approach is to define an Environment variable for the input in the Pre-request Script tab, provide a script to set the value for the defined variable and use the variable in URL to pass as an input to API.
• Script in Pre-request script executes before the GET request is submitted. Logic can be written here to provide random values for the variables – ex- generate random numbers on each request and based on the number choose a value for the term

Manual Testing – Test results

• Test results can be captured in Test Tab. The Test tab executes after the API call is processed, scripts can be written here to check the status of the requests, retrieve the data from response object etc. ex in below shows checking status code of 200 and checking the JSON object length to see if any data exists or not.

Collections Runner

• Collections are set of tests grouped by API’s. Collections can be run manually or scheduled by monitors to be run at specific time/day. NYU-API’s collection which contains tests for different API’s grouped in API specific folder
• Collections Runner is used to run tests available for API’s in the collection, it can be done as a single iteration or multiple iterations.

Collections Runner – Test data from file

• Input data to tests in collections runner can be passed as shown earlier in Pre-request Scripts, test tabs.
• Input can also be passed to collection runner from a CSV file or JSON file so that multiple iterations can run on different set of data.
• To read input data from CSV or JSON file the file path/name needs to be specified in the Data section of the Collection runner window and also script needs to written to read from the files. Sample script to read values of term from csv file.

Newman – CLI of Postman

• Newman is command line interface of postman, this is used to run collections from command line.
• Newman needs to be installed from command line using Node JS npm
• Newman can be easily integrated with Jenkins to automate tests as part of CI/CD
• Sample Neman command line script – newman run NYU.json -e Sandbox.postman_environment.json -k –timeout-script=100000
  • NYU.json is the collection which is being executed
  • Sandbox.postman_environment.json – Is the environment specific variables used for running the collection
  • -k is to suppress SSL
  • –timeout is the time out interval for the entire script
• All other command line options can be found at Newman Command Line options
• Jenkins integration with newman – Jenkins-Newman setup