Software Testing - Estimation Techniques

Software test estimation is the process of predicting the time, effort, and resources required for testing activities. It considers project size, complexity, risks, and team capability to create a realistic testing plan.

• Test planning and execution are controlled.
• Test design and analysis are performed during the testing process.
• Test execution and evaluation are carried out during the testing phase.
• Test closure and reporting are done after testing is completed.

Key Elements to Estimate in Software Testing

When estimating software testing, there are several key factors to consider:

• Time: Estimate how long testing will take to meet deadlines and SLAs. Proper planning ensures timely delivery without delays.
• Resources: Include team, tools, and equipment required for testing. Efficient use prevents wastage and improves productivity.
• Cost: Define the budget for the testing phase and manage expenses. Accurate estimation avoids overspending and keeps the project on track.
• Skillset: Consider team experience and expertise while assigning tasks. Skilled members complete work faster and more accurately.
• Risks: Identify possible challenges like technical issues or delays early. Planning for risks helps reduce their impact on timeline and cost.

Steps to Perform Test Estimation

Test estimation is typically performed in four simple steps:

Step 1. Divide the Project into Small Tasks

Use the Work Breakdown Structure (WBS) to break a large project into smaller, manageable tasks in a top-down manner. This helps simplify complex testing work and improves estimation accuracy.

• Break project into modules, sub-modules, and functionalities
• Suitable for large and complex projects
• Follows a top-down approach: goal -> deliverables -> activities -> tasks
• Makes tasks independent and easier to estimate and manage

Step 2. Allocate each task to suitable team members

After breaking the project into smaller tasks, assign each task to suitable team members based on their skills, experience, and expertise. This ensures efficient execution and better quality output.

• Assign tasks based on skillset and experience
• Ensure balanced workload among team members
• Improves efficiency and accountability in execution

Step 3. Estimate the effort required to complete each task

Estimate the time and effort required for each task using techniques like Three-Point Estimation or Function Point Analysis. This helps improve accuracy by considering different scenarios and task complexity.

1. Three-Point Estimation (PERT)

Three-Point Estimation is used to estimate effort using three possible scenarios: Optimistic, Most Likely, and Worst case. It provides a realistic estimate by reducing uncertainty.

Scenarios:

• Optimistic (O): Best possible case
• Most Likely (M): Normal expected case
• Worst (W): Worst possible case

Formula: E = (O + 4M + W) / 6

Example: Estimation of login feature effort using different scenarios.
Given: O = 2 hrs, M = 4 hrs, W = 6 hrs
Calculation:
E = (2 + 4×4 + 6) / 6 = 4 hrs

Estimated Effort: 4 hours (approx.)

2. Function Point Analysis (FP)

Function Point Analysis estimates effort based on system functionality and complexity. Each module is assigned points based on difficulty level (Easy, Medium, Hard).

• Assign points to each function based on complexity
• Add all function points
• Multiply with cost per FP to get total effort

Example: Login (Easy) = 2 FP, Dashboard (Medium) = 3 FP, Payment (Hard) = 5 FP
Total FP = 2 + 3 + 5 = 10
If 1 FP = $10 → Total Cost = $100Step

4. Validate the estimation

This step ensures that the prepared effort estimates are reviewed and confirmed for accuracy, feasibility, and alignment with project goals.

• Estimates are reviewed with managers and stakeholders
• Accuracy, risks, and missing factors are checked
• Final approval ensures realistic and achievable planning

Software Test Estimation Techniques

Estimating time, effort, and resources for testing ensures efficient execution and alignment with project goals. Below are commonly used techniques.

• Work Breakdown Structure (WBS): Breaks testing work into smaller manageable tasks for better planning and control. It improves estimation accuracy and resource allocation.
• Functional Point Analysis (FP): Estimates effort based on system functionality and complexity using functional points. It helps in measuring project size systematically.
• Wideband Delphi Technique: Uses multiple experts to estimate effort through discussion and consensus. It improves accuracy by combining different expert opinions.
• Three-Point Estimation (PERT): Uses optimistic, most likely, and pessimistic values to estimate effort. It reduces uncertainty and gives a balanced estimate.
• Use-Case Based Estimation: Estimates effort based on user interactions and system use cases. It is useful in early phases of development.
• Percentage Distribution: Divides total testing effort into different phases using predefined percentages. It is simple and quick for estimation.
• Ad-Hoc Estimation: Based on experience, intuition, and quick judgment without formal methods. It is useful for small or urgent tasks.

Test Estimation Best Practices

Test estimation becomes more accurate and reliable when teams follow structured practices like proper planning, learning from past projects, and considering real-world uncertainties.

• Resource Planning Ensure proper allocation of people, tools, and timelines
• Use Past Experience Refer to previous projects to improve estimation accuracy
• Add Buffer Time Account for risks like delays, defects, or team changes
• Stick to Estimates Avoid frequent changes unless major requirements change
• Consider Bug Cycle Include time for defect fixing and re-testing
• Define Project Scope Clearly understand the size and complexity of the project
• Plan for Load and Parallel Testing Include performance and version comparison efforts in estimates