Security Testing: Best Practices for Ensuring Quality

Security testing, often referred to as application security testing (AST), is a critical component of the software development process. It focuses on evaluating the security protocols of an application to identify potential vulnerabilities and weaknesses in its data protection mechanisms.

AST enhances software quality and reliability through a mix of manual and automated testing methods, including code analysis, penetration testing, and other security checks.

Objectives of security testing

As the name implies, security testing aims to fulfill a clear set of objectives:

• Identify potential threats and vulnerabilities within the software system.
• Ensure security measures effectively protect data and comply with relevant laws, regulations, and industry standards.
• Integrate appropriate security tests throughout the software development lifecycle (SDLC).
• Assign identified bugs and vulnerabilities to the appropriate personnel, QA testers or security specialists, for resolution.
  

Security testing is a collaborative effort across development, security, and operations teams. In some cases, non-specialists may also participate in exploratory testing. By observing how first-time users interact with the application, teams can uncover potential security issues and gaps in the user experience.

Security testing methods

Given the importance of security in modern software workflows, a variety of techniques are used to uncover and address vulnerabilities. Below are some of the most common methods.

Vulnerability Scanning

Vulnerability scanning is a foundational technique in any security testing strategy. It identifies weaknesses in software systems and networks that could be exploited by attackers. This method plays a key role in managing cyber risks, protecting sensitive data, and ensuring regulatory compliance.

Penetration testing

Penetration testing or pen testing simulates real-world cyberattacks on a software system to assess its overall security posture. The goal is to identify vulnerabilities that could be exploited under real conditions.

Pen testing isn’t always mandatory; its use depends on industry standards, regulatory requirements, and the nature of the application being tested.

Key aspects of penetration testing include:

• Simulating real-world cyberattacks to evaluate how effectively the system can detect and respond to threats.
• Identifying weaknesses such as insecure configurations, weak authentication mechanisms, unpatched software, and improper input validation.
• Combining automated tools with manual review for thorough analysis and verification.
• Producing detailed reports that outline identified vulnerabilities, associated risk levels, potential impacts, and recommended remediation steps.

Open-box testing / White Box Penetration Testing

White box penetration testing, sometimes called open-box, crystal box, or oblique box testing, is a method in which the tester is given full access to the target system’s internal structure. This includes source code, architecture diagrams, credentials, and network maps.

By providing complete transparency, this type of test simulates an attack from an internal threat actor or a highly informed external attacker. The goal is to evaluate how the system holds up against targeted attacks using as many vectors as possible, often with the added benefit of reducing testing time and cost.

This approach is particularly useful for identifying complex security flaws such as insecure APIs, logic vulnerabilities, or authentication issues that might be missed in more opaque testing models.

Closed Box Penetration Testing

Closed box penetration testing or black box testing, sometimes called single-blind testing, is a method where the tester has no prior knowledge of the application’s internal structure, code, or configurations. The only information typically provided is the name of the target organization or system.

This approach simulates an external attacker attempting to breach the system without insider access. Testers rely entirely on publicly available information and surface-level interactions to identify potential vulnerabilities, such as exposed services, weak endpoints, or flawed authentication flows.

Because the tester operates without any internal context, closed box testing offers a realistic assessment of how a system would stand up to a real-world attack from an uninformed threat actor.

Covert testing

Covert testing is a specialized type of penetration test or security audit conducted without the knowledge of system administrators or security personnel (except for a select few individuals with high-level authorization).

The goal is to simulate a real-world cyberattack and observe how the organization responds when unaware they’re being tested. This method is especially effective at evaluating monitoring, alerting, and incident response systems in an uncontrolled, unscripted environment.

Key characteristics of covert testing:

• Conducted in secret to provoke authentic responses from security systems and personnel.
• Authorized by executive-level management but kept confidential from IT and security teams.
• Simulates attacks by both internal and external threat actors.
• Measures how quickly and effectively the system can detect and respond to real intrusions.
• Helps uncover blind spots in monitoring and response protocols that might be missed during standard testing.

External security testing

External security testing evaluates a software system’s defenses against external threats—typically from ethical hackers or other actors attempting to access protected data such as websites or public-facing network servers.

Testers simulate real-world attacks to assess how well the system can withstand unauthorized intrusion attempts. This often involves techniques like port scanning, vulnerability scanning, penetration testing, and web application attacks to measure overall system resilience.

Key characteristics of external security testing:

• Testers operate entirely outside the internal system and source code, mimicking the perspective of an external attacker.
• They conduct tests without prior knowledge of the system’s architecture, codebase, or internal structure.
• Evaluates the strength of firewalls, intrusion detection and prevention systems, security configurations, and access controls.

Internal security testing

Internal security testing, sometimes referred to as an internal audit, focuses on evaluating an application’s data defense mechanisms from within the organization. It simulates potential threats from insiders, such as employees, contractors, or compromised users who already have some level of system access.

Key characteristics of internal security testing:

• Simulates insider threats to assess how the system protects sensitive data from users with legitimate access credentials, internal IP addresses, or physical network access.
• Often mimics scenarios like privilege escalation, lateral movement, and data exfiltration.
• Attacks are launched from within the corporate firewall.
• Testers have partial or full knowledge of the system.
• Helps uncover internal vulnerabilities such as weak access controls, unpatched internal services, overly permissive user roles, and insecure database access.

API security testing

APIs are critical to the day-to-day operations of modern IT systems. However, their widespread use also introduces potential security risks, such as misconfigurations, weak authentication, and improper usage. Because APIs often provide direct access to valuable and sensitive data, they are a prime target for attackers.

API security testing helps mitigate these risks by simulating various interactions with APIs and monitoring their responses for vulnerabilities. This includes testing RESTful and SOAP APIs, as well as GraphQL endpoints, to uncover gaps in authentication, data handling, and overall security.

Key characteristics of API security testing:

• Focuses on interface-level security, checking for proper authentication, authorization, and data protection mechanisms.
• Validates API behavior against common threats such as injection attacks, broken authentication, session mismanagement, excessive data exposure, and lack of rate limiting.
• Uses a range of techniques including authentication and authorization testing, input fuzzing, and rate limit tests.

Input validation testing

Input validation testing ensures that an application properly checks and filters user input to prevent malicious data from being processed. It verifies that input data (such as formats, lengths, and ranges) meets expected criteria to help prevent threats like SQL injection, remote code execution, and cross-site scripting (XSS).

Key characteristics of input validation testing:

• Evaluates how the application handles input across the client-side, server-side, and API layers, ensuring only safe and correctly formatted data is accepted.
• Identifies vulnerable entry points such as forms, input fields, search boxes, login pages, URL parameters, headers, cookies, and JSON/XML data in APIs.
• Validates whether input data complies with defined rules for format, content, and value range.
• Assesses the effectiveness of input sanitization systems in filtering or neutralizing malicious input.
• Employs techniques like fuzz testing, boundary value testing, injection testing, and filter bypass testing.

Security testing frameworks

The tests we’ve covered so far are most effective when guided by a clear structure. That’s where security testing frameworks come in. These frameworks help teams plan, prioritize, and standardize their efforts so testing is consistent and comprehensive.

SAST (Static Application Security Testing)

SAST is a security testing approach that analyzes an application’s source code without executing it. The goal is to catch vulnerabilities like input validation issues, SQL injections, or buffer overflows, early in the development process, before the code is ever run.

Static analysis uses techniques such as code review, data flow analysis, and automated scanning to identify potential security flaws in the codebase. It’s especially useful for spotting issues at the code level that could lead to serious vulnerabilities if left unchecked.

DAST (Dynamic Application Security Testing)

DAST evaluates a software application while it’s running, simulating external attacks to uncover security vulnerabilities in real time. Instead of analyzing source code, it tests the application from the outside, just like a real attacker would.

Common techniques include vulnerability scanning, penetration testing, and data flow analysis. Testers use these methods to probe for weaknesses in the system’s architecture and observe how the application responds to potential threats during execution.

DAST tools help detect issues like cross-site scripting (XSS), SQL injection, and insecure server configurations, vulnerabilities that may only appear under real-world conditions.

While SAST tools analyze code statically, DAST tools assess application security dynamically, making them essential for identifying runtime threats.

IAST (Interactive Application Security Testing)

IAST combines elements of SAST and DAST to deliver real-time analysis of a software application while it’s running.

Tests are typically executed in a QA environment, where IAST tools use agents and sensors to monitor the application’s behavior and highlight questionable lines of code in the post-build codebase. These tools often generate alerts to notify teams of issues that require immediate attention.

SCA (Software Composition Analysis)

SCA evaluates any third-party components used in an application’s day-to-day functioning. It works to find potential security gaps in those components and recommend remediation strategies.

For example, SCA can detect vulnerabilities in commonly used open-source libraries like Log4j, Spring Boot, or jQuery.

SCA comprises both manual and automated tests and contributes directly to shift-left testing in a development ecosystem. This framework targets the application codebase, revealing the health of processes that support open-source software usage. 

SCA can, for example, detect all open-source components in the code, their license compliance data, and ferret out common problems with security configurations.

RASP (Runtime Application Self-Protection)

RASP safeguards software applications by analyzing their behavior in real-time as an additional layer of data protection. It studies how the application can detect and prevent threats to data security in real-time.

RASP is performed to identify application responses to malicious activity that may not be prevented by traditional security filters like firewalls, antivirus installations, and intrusion detection systems.

MAST (Mobile Application Security Testing)

MAST identifies security flaws specific to mobile apps by analyzing code, storage, encryption, API usage, and risks like rooted device access.

It combines elements of SAST, DAST, forensic analysis, and behavior analysis to evaluate how apps behave during runtime and how they handle sensitive data. MAST also ensures compliance with Google Play and Apple App Store guidelines.

For example, it can detect unsecured local data storage, where sensitive information is left unencrypted and accessible on the device. Unlike general frameworks, MAST addresses mobile-specific attack vectors and device-level risks that others may miss.

Best practices for security testing

Security testing covers a wide range of areas in modern software development. To ensure thorough coverage and effective results, teams should follow a set of best practices that help maximize both code quality and test effectiveness.

Standardize test cases

By standardizing test cases, QA teams can build consistent, repeatable, and effective evaluations of security vulnerabilities. A few guidelines to do so are:

Define the objectives of the security test

Clarify goals by listing common vulnerabilities. Set down metrics for data confidentiality, availability, and integrity, as well as benchmarks for compliance ( GDPR, PCI-DSS, HIPAA).

Create effective test cases

Create effective test cases based on predetermined frameworks — OWASP Top 10 (e.g., SQL Injection, Broken Access Control), NIST 800-53 / 800-115, ISO/IEC 27001/27034, SANS CWE Top 25.

Build a test case template for a consistent structure. 

Here’s a quick example:

Categorize tests based on the type of vulnerability or component under test

Common vulnerability types:

• Injection attacks (e.g., SQL, XSS, Command Injection)
• Authentication flaws
• Access control issues
• Insecure configurations
• Sensitive data exposure

Common components under test:

• APIs
• Web forms
• File uploads
• Mobile endpoints
• Database queries

Use automation whenever possible 

Use automation whenever possible for standard checks. Use SAST tools for code-level issues, DAST tools for runtime threats, and SCA tools for 3rd party library analyis.

More best practices

• Record all tests in a version-controlled repository and dashboard.
• Put test cases through peer reviews. Update them based on new threats and code changes.
• Map each test case to risk categories and compliance requirements.

Image: Test case versioning in TestRail Enterprise allows users to compare any two test case versions side-by-side and see highlighted differences between the two versions. 

Security test case example:

Choose the right testing tools

Selecting the right testing tools is essential for building a strong, scalable, and effective application security strategy. Your tools should align with your team’s tech stack, security goals, compliance requirements, and DevOps workflows.

Start by identifying your testing needs

Begin with an analysis of the types of vulnerabilities and risks your application may face. This will help you determine what kinds of tests and evaluations are required—such as code-level analysis, runtime assessments, API testing, or third-party dependency scans.

Once those needs are clearly defined, you can evaluate tools and frameworks that best support those specific testing goals.

Common capabilities to look for may include:

• SAST (Static Application Security Testing)
• DAST (Dynamic Application Security Testing)
• API security testing
• Open source risk management (SCA
• Compliance with legal and industry standards

Integration Considerations

Look for tools that integrate easily into your existing DevOps pipeline. They should:

• Support API access
• Offer IDE plugins
• Provide actionable bug resolution guidance

Evaluate Core Capabilities

When assessing tools, ask:

• Does it minimize false positives and negatives?
• Is the UI intuitive, and is onboarding straightforward?
• Does it support the types of applications you’re testing?
• Does it impact application performance during testing?
• Does it generate useful, customizable reports?
• Does it align with standards like OWASP, PCI-DSS, or HIPAA?

Budget Fit:

Make sure the tool fits your budget. Options range from open-source tools to enterprise-grade solutions.

Document results

Document all test results meticulously. All stakeholders should have access to documents so that relevant teams are up to date on project status.

A tool like TestRail will automatically record and catalog test results into predetermined formats. You’ll have complete visibility into manual, exploratory, and automated tests in a centralized dashboard. So, this won’t be too much effort with the right tool.

Design separate report metrics for technical and non-technical stakeholders. Engineers need effective, clear, and concise language that tells them what’s wrong and needs fixing. Business managers and sales personnel need to know about the real-world impact (short and long-term).

At the very least, include:

• An overview of the test pipeline
• Key findings and insights
• Suggestions for resolving security anomalies
• Screenshots, log files, and vulnerability reports
• Actionable recommendations for further steps (to be taken by the report stakeholder)

Implement test-driven development

Test-driven development (TDD) helps build more secure apps by integrating security checks into the development workflow. It’s also an essential element in establishing shift-left testing — test and find bugs earlier in the pipeline — principles in the context of security testing.

Note: Test-Driven Development (TDD) is primarily a development approach. Security considerations should be incorporated from the beginning of the development process to enable TDD within the ambit of security testing. In other words, security is not an afterthought but an integral part of TDD practices.

Encourage devs to build tests (some of them, at least) before writing the code. They write a test that fails, then write code to pass the failed test, and finally refactor the code while maintaining test success.

By doing so, devs think more proactively about input validation, authentication, and access control before  coding. They consider requirements from the coding stage, contributing to faster bug detection. It also results in more testable, modular, and maintainable codebases.

Improve QA collaboration with TestRail

TestRail offers a robust set of features designed to support, manage, and scale security testing efforts across teams. Whether you’re working in a centralized or distributed environment, TestRail helps QA professionals, security testers, and project managers stay aligned and informed.

Key capabilities include:

• Centralized visibility and control to support compliance, governance, and auditing.

• Secure access to testing data, whether your team is co-located or globally distributed.
  
• Security policy enforcement through single sign-on (SSO) with SAML 2.0, OAuth, and OpenID Connect, along with support for email and authenticator app-based login.
  
• Role-based access control to manage user permissions at both global and project levels.
  
• Real-time collaboration via integration with tools like Slack, ensuring everyone has access to the latest updates and insights.

• Audit-friendly tracking, with full visibility into every item created, updated, or removed from your TestRail instance.
  
• Powerful API support to fetch, add, and manipulate nearly any test entity or artifact programmatically.
  

TestRail also supports deeper integration into CI/CD pipelines through the TestRail Command Line Interface (TRCLI). This allows teams to push automated test results, including security test outcomes, directly into TestRail. By integrating TRCLI into your pipeline, you can ensure consistent visibility into test results, streamline traceability, and improve collaboration between QA and security teams.

Start your 30-day free trial of TestRail’s comprehensive test management platform today! .