SDET Interview Questions And Answers (Complete Guide)

Read this comprehensive guide on SDET interviews to understand the format and learn how to answer commonly asked SDET interview questions:

This tutorial provides an overview of commonly asked interview questions for SDET roles. It also covers the general interview format and provides tips to excel in the interviews.

The coding problems in this tutorial are explained using Java, but SDET tutorials are typically language agnostic, and interviewers are usually flexible with the choice of programming language.

SDET Interview Preparation Guide

SDET interviews, in most of the top product companies, are quite similar to how interviews are conducted for development roles. SDETs are expected to have a broad understanding similar to developers.

However, SDET interviews focus on critical thinking skills and hands-on experience in coding, along with an eye for quality and detail.

Here are some points to focus on while preparing for an SDET interview:

• Be willing to learn new technologies and leverage existing skills, as SDET interviews are often technology/language agnostic.
• Develop good communication and team skills, as SDET roles require communication and collaboration with multiple stakeholders.
• Understand system design concepts, scalability, concurrency, non-functional requirements, etc.

In the sections below, we will discuss the general format of an SDET interview and provide sample questions to help you prepare.

Format Of Software Development Engineer in Test Interview

Most companies have their preferred format for interviewing candidates for SDET roles. The interview format may vary based on the specific requirements of the team and the role.

However, the general theme of SDET interviews is based on the following:

• Telephonic discussion: Initial conversation with the manager and/or team members to assess fit.
• Written round: Questions related to testing and test cases.
• Coding proficiency round: Simple coding questions (language agnostic) to test coding skills and understanding of constructs like edge scenarios and null checks.
• Understanding of basic development concepts: Questions about OOPS Concepts, SOLID Principles, etc.
• Test Automation Framework design and development.
• Scripting languages: Selenium, Python, Javascript, etc.
• Culture fit/HR discussion and negotiations.

SDET Interview Questions And Answers

In this section, we will discuss sample questions and detailed answers for different categories that are commonly asked in SDET interviews.

Coding Proficiency

This round tests coding skills, including the ability to handle coding constructs, edge scenarios, and null checks.

Occasionally, interviewers may also ask candidates to write unit tests for the code they write.

Let’s see a few sample coding problems and their solutions:

Q #1) Write a program to swap two numbers without using a temporary variable.

Answer:

Program to swap two numbers:

public class SwapNumbers {

  public static void main(String[] args) {
    System.out.println("Calling swap function with inputs 2 & 3");
    swap(2,3);
    System.out.println("Calling swap function with inputs -3 & 5");
    swap(-3,5);
  }
  
  private static void swap(int x, int y) {
    System.out.println("Values before swap: " + x + " and " + y);
    // swap logic
    x = x + y;
    y = x - y;
    x = x - y;
    System.out.println("Values after swap: " + x + " and " + y);
  }
}

Output of the above code snippet:

After submitting the solution, it is recommended to dry run the code for multiple inputs to ensure it is correct. Let’s try it for positive and negative values.

Positive values: X = 2, Y = 3

 // swap logic - x=2, y=3
x = x + y; => x=5
y = x - y; => y=2
x = x - y; => x=3 
x & y swapped (x=3, y=2)

Negative values: X = -3, Y = 5

// swap logic - x=-3, y=5
x = x + y; => x=2
y = x - y; => y=-3
x = x - y; => x=5
x & y swapped (x=5, y=-3)

Q #2) Write a program to reverse a number.

Answer:

Program to reverse a number:

public class ReverseNumber {
  public static void main(String[] args) {
    int num = 10025;
    System.out.println("Input - " + num + " Output: " + reverseNo(num));
  }  

public static int reverseNo(int number) {
    int reversed = 0;    
   while(number != 0) {
      int digit = number % 10;
      reversed = reversed * 10 + digit;
      number /= 10;
    }
    return  reversed;
  }
}

Output for this program with input 10025 would be 52001

Q #3) Write a program to calculate the factorial of a number.

Answer:

Factorial is a common question in interviews. For SDET interviews, it’s important to handle edge scenarios like max values, min values, negative values, etc.

Here’s a program for factorial using recursion and for-loop:

public class Factorial {

  public static void main(String[] args) {

    System.out.println("Factorial of 5 using loop is: " + factorialWithLoop(5));
    System.out.println("Factorial of 10 using recursion is: " + factorialWithRecursion(10));
    System.out.println("Factorial of a negative number -100 is: " + factorialWithLoop(-100));

  }

  public static long factorialWithLoop(int n) {
    if(n < 0) {
      System.out.println("Negative numbers do not have a factorial");
      return -9999;
    }
    long fact = 1;
    for (int i = 2; i <= n; i++) {
      fact = fact * i;
    }
    return fact;
  }

  public static long factorialWithRecursion(int n) {
    if(n < 0) {
      System.out.println("Negative numbers do not have a factorial");
      return -9999;
    }

    if (n <= 2) {
      return n;
    }
    return n * factorialWithRecursion(n - 1);
  }

}

Output of the above code:

Q #4) Write a program to check whether a given string has balanced parentheses?

Answer:

Approach: The problem is slightly complex and requires the candidate to think beyond coding constructs. The interviewer is looking for the ability to use the right data structure for the problem at hand.

Balanced parentheses means that a given string containing parentheses (or brackets) should have equal opening and closing counts and be well-structured.

You can use a stack data structure to solve this problem. A stack is a LIFO (Last In First Out) data structure, similar to a stack of plates where the topmost plate is used first.

Algorithm:

#1) Declare a Character Stack (which holds the characters in the string and performs push and pop operations).

#2) Traverse through the input string:

• If an opening bracket character is encountered (such as ‘[‘, ‘{‘, ‘(‘), push it onto the stack.
• If a closing bracket character is encountered (such as ‘]’, ‘}’, ‘)’), pop an element from the stack and check if it matches the corresponding opening bracket character. If the popped element does not match the opening bracket, the string is not balanced. If all brackets are properly matched, the stack will be empty at the end.

import java.util.Stack;

public class BalancedParantheses {

  public static void main(String[] args) {

    final String input1 = "{()}";
    System.out.println("Checking balanced parantheses for input: " + input1);

    if (isBalanced(input1)) {
      System.out.println("Given string is balanced");
    } else {
      System.out.println("Given string is not balanced");
    }
  }

  /**
   * Checks if a string has balanced parentheses or not
   * @param input_string the input string
   * @return true if the string has balanced parentheses, false otherwise
   */
  private static boolean isBalanced(String input_string) {

    Stack stack = new Stack<>();

    for (int i = 0; i < input_string.length(); i++) {

      switch (input_string.charAt(i)) {
        case '[':
        case '(':
        case '{':
          stack.push(input_string.charAt(i));
          break;
        case ']':
          if (stack.empty() || !stack.pop().equals('[')) {
            return false;
          }
          break;
        case '}':
          if (stack.empty() || !stack.pop().equals('{')) {
            return false;
          }
          break;
        case ')':
          if (stack.empty() || !stack.pop().equals('(')) {
            return false;
          }
          break;
      }
    }

    return stack.empty();
  }
}

The output of the above code:

Solving these coding problems requires more than just knowledge of coding constructs. It also requires the ability to think critically and use appropriate data structures and algorithms.

Test Automation Framework Related

This round focuses on test automation framework design and development. Interviewers may ask questions about framework design, advantages and disadvantages of different approaches, and related topics.

Here are some sample questions and solutions for this round:

Q #5) Explain and design the components of an automation framework for a web application.

Answer:

When answering this question, consider the following:

• Talk about different types of frameworks, such as data-driven, keyword-driven, and hybrid frameworks.
• Mention the Page Object Model for storing page/module details.
• Discuss common modules like helper functions, utilities, and loggers.
• Talk about reporting modules and integrating reports with email and scheduling tests.

Recommended Reading: Most Popular Test Automation Frameworks

Q #6) Explain testing strategies for a mobile application.

Answer:

When answering this question, consider the following:

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ul>

Discuss testing on devices versus emulators.

Mention strategies for identifying and storing objects/elements on different screens using the Page Object Model.

Talk about load testing a mobile application.

Discuss

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