Reading test data from JSON in Selenium Python - Test Execution Trace

Test Overview

This test reads user login data from a JSON file and verifies successful login on a web page.

Test Code - Selenium

Selenium Python

import json
import unittest
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

class TestLoginWithJSON(unittest.TestCase):
    def setUp(self):
        self.driver = webdriver.Chrome()
        self.driver.get('https://example.com/login')

    def test_login(self):
        with open('testdata.json', 'r') as file:
            data = json.load(file)
        username = data['username']
        password = data['password']

        driver = self.driver
        WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.ID, 'username')))
        driver.find_element(By.ID, 'username').send_keys(username)
        driver.find_element(By.ID, 'password').send_keys(password)
        driver.find_element(By.ID, 'login-btn').click()

        WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.ID, 'welcome-msg')))
        welcome_text = driver.find_element(By.ID, 'welcome-msg').text
        self.assertIn('Welcome', welcome_text)

    def tearDown(self):
        self.driver.quit()

if __name__ == '__main__':
    unittest.main()

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser opens	Browser window opens at https://example.com/login page	—	PASS
2	Reads username and password from testdata.json file	JSON file loaded with keys 'username' and 'password'	—	PASS
3	Waits until username input field is present	Username input field visible on login page	Presence of element located by ID 'username'	PASS
4	Enters username and password into input fields	Username and password fields filled with test data	—	PASS
5	Clicks the login button	Login button clicked, page starts loading	—	PASS
6	Waits until welcome message element is present	Welcome message element visible on page	Presence of element located by ID 'welcome-msg'	PASS
7	Checks that welcome message contains 'Welcome'	Welcome message text retrieved	Assert 'Welcome' in welcome message text	PASS
8	Test ends and browser closes	Browser window closed	—	PASS

Failure Scenario

Failing Condition: The JSON file is missing or malformed, or the login fails due to incorrect credentials

Execution Trace Quiz - 3 Questions

At which step does the test read the login data from the JSON file?

A Step 6

B Step 4

C Step 2

D Step 1

Key Result

Reading test data from external JSON files helps separate test logic from data, making tests easier to maintain and reuse.

Practice

1. What is the main benefit of reading test data from a JSON file in Selenium Python tests?

easy

A. It encrypts test data for security.

B. It makes tests run faster by avoiding web interactions.

C. It automatically generates test cases without writing code.

D. It keeps test code clean and makes data easy to update without changing code.

Solution

1. Step 1: Understand test data separation

   Reading test data from JSON separates data from test logic, making code cleaner.

2. Step 2: Recognize flexibility advantage

   Updating test data in JSON does not require changing test scripts, improving flexibility.

3. Final Answer:

   It keeps test code clean and makes data easy to update without changing code. -> Option D

4. Quick Check:

   Data separation = Clean code + Easy updates [OK]

Hint: Separate data from code for easy updates [OK]

Common Mistakes:

• Thinking JSON speeds up test execution
• Believing JSON auto-generates tests
• Confusing data storage with encryption

2. Which Python code snippet correctly reads a JSON file named data.json into a variable test_data?

easy

A. import json
test_data = json.load(open('data.json'))

B. test_data = open('data.json').read()

C. import json
test_data = json.loads('data.json')

D. test_data = json.read('data.json')

Solution

1. Step 1: Identify correct json module usage

   The json.load() function reads JSON from a file object, so open() must be passed to json.load().

2. Step 2: Check syntax correctness

   import json test_data = json.load(open('data.json')) correctly imports json and uses json.load(open('data.json')) to read the file.

3. Final Answer:

   import json\ntest_data = json.load(open('data.json')) -> Option A

4. Quick Check:

   json.load + open(file) = correct JSON read [OK]

Hint: Use json.load() with open() for files [OK]

Common Mistakes:

• Using json.loads() on filename string
• Forgetting to import json module
• Calling non-existent json.read() function

3. Given the JSON file user.json with content:

{"username": "testuser", "password": "pass123"}

and the code:

import json
with open('user.json') as f:
    data = json.load(f)
print(data['username'])

What will be the output?

medium

A. {'username': 'testuser', 'password': 'pass123'}

B. pass123

C. testuser

D. KeyError

Solution

1. Step 1: Load JSON data into dictionary

   The json.load(f) reads the JSON file and converts it into a Python dictionary with keys 'username' and 'password'.

2. Step 2: Access dictionary value by key

   data['username'] accesses the value 'testuser' from the dictionary.

3. Final Answer:

   testuser -> Option C

4. Quick Check:

   data['username'] = 'testuser' [OK]

Hint: Access JSON keys like dictionary keys [OK]

Common Mistakes:

• Printing the whole dictionary instead of key value
• Using wrong key causing KeyError
• Confusing json.load() with json.loads()

4. What is wrong with this code snippet that reads JSON test data?

import json
file = open('data.json')
data = json.load(file)
file.close()
print(data['email'])

Assuming data.json does not contain the key email.

medium

A. The code will raise a KeyError because 'email' key is missing.

B. The print statement syntax is incorrect.

C. The file is not closed properly.

D. json.load() cannot read from open file objects.

Solution

1. Step 1: Understand json.load() behavior

   json.load() correctly reads JSON from an open file object, so no error here.

2. Step 2: Identify missing key issue

   Accessing data['email'] when 'email' key is missing causes a KeyError at runtime.

3. Final Answer:

   The code will raise a KeyError because 'email' key is missing. -> Option A

4. Quick Check:

   Missing key access = KeyError [OK]

Hint: Check keys exist before accessing JSON data [OK]

Common Mistakes:

• Thinking json.load() fails on open files
• Ignoring possible missing keys in JSON
• Assuming file.close() is missing or wrong

5. You want to use JSON test data to fill a login form in Selenium Python. The JSON file login.json contains:

{"username": "user1", "password": "pass1"}

Which code snippet correctly reads the JSON and uses Selenium to fill the form fields with ids user and pass?

hard

A. import json
with open('login.json') as f:
data = json.load(f)
driver.find_element_by_name('user').send_keys(data['username'])
driver.find_element_by_name('pass').send_keys(data['password'])

B. import json
with open('login.json') as f:
data = json.load(f)
driver.find_element('id', 'user').send_keys(data['username'])
driver.find_element('id', 'pass').send_keys(data['password'])

C. import json
with open('login.json') as f:
data = json.loads(f)
driver.find_element_by_id('user').send_keys(data['username'])
driver.find_element_by_id('pass').send_keys(data['password'])

D. import json
with open('login.json') as f:
data = json.load(f)
driver.find_element('name', 'user').send_keys(data['username'])
driver.find_element('name', 'pass').send_keys(data['password'])

Solution

1. Step 1: Correctly read JSON file

   json.load(f) reads JSON from file object correctly; json.loads() expects a string, so import json with open('login.json') as f: data = json.loads(f) driver.find_element_by_id('user').send_keys(data['username']) driver.find_element_by_id('pass').send_keys(data['password']) is wrong.

2. Step 2: Use correct Selenium locator method

   driver.find_element('id', 'user') is the modern syntax to find element by id; find_element_by_id() is deprecated.

3. Step 3: Match locators with element ids

   The form fields have ids 'user' and 'pass', so locating by id is correct, not by name.

4. Final Answer:

   import json with open('login.json') as f: data = json.load(f) driver.find_element('id', 'user').send_keys(data['username']) driver.find_element('id', 'pass').send_keys(data['password']) -> Option B

5. Quick Check:

   json.load + find_element('id', ...) = correct usage [OK]

Hint: Use json.load() and find_element('id', ...) for form filling [OK]

Common Mistakes:

• Using json.loads() on file object
• Using deprecated find_element_by_id()
• Using wrong locator type (name instead of id)