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  <front>
    <journal-meta>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>of Secondary Study on the Verification and Validation of Blockchain Applications: Preliminary Results</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Mitja Gradišnik</string-name>
          <email>mitja.gradisnik@um.si</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Tina Beranič</string-name>
          <email>tina.beranic@um.si</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Muhamed Turkanović</string-name>
          <email>muhamed.turkanovic@um.si</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Workshop</string-name>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Maribor, Slovenia</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Faculty of Electrical Engineering and Computer Science - University of Maribor</institution>
          ,
          <addr-line>Koroška cesta 46, Maribor</addr-line>
          ,
          <country country="SI">Slovenia</country>
        </aff>
      </contrib-group>
      <fpage>3</fpage>
      <lpage>15</lpage>
      <abstract>
        <p>In recent years, the development of blockchain technologies, especially programmable smart contracts, has experienced an exceptional growth. This growth is mainly due to the potential these technologies show in various industrial fields. Due to the recognized numerous advantages of blockchain for business environments, there arises a need for their introduction into software solutions, which must be built with high quality to be useful for users. A growing body of literature is found addressing validation and verification techniques. In this paper we conduct review of secondary studies. We conducted an systematic literature review of secondary studies to gain a more refined understanding of good practices for quality assurance, from which conclusions could improve the development process of blockchain-based applications. The systematic search yielded 377 studies of which 37 are selected for further analysis. The literature review revealed that, in quality assurance, formal verification techniques and static analysis are important alongside testing. Due to the immutability of smart contracts, it is recommended to use techniques complementarily. The analysis of individual internal quality aspects revealed that most attention in research field was paid to security, as this is the key attribute that determines whether the implementation of blockchain-based software solutions achieves its intended goals.</p>
      </abstract>
      <kwd-group>
        <kwd>Blockchain-based apps</kwd>
        <kwd>smart contracts</kwd>
        <kwd>verification</kwd>
        <kwd>validation</kwd>
        <kwd>testing</kwd>
        <kwd>security</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        In recent years, blockchain technologies have attracted significant attention from academia and industry,
as they can fundamentally transform how businesses operate [
        <xref ref-type="bibr" rid="ref1 ref2">1, 2</xref>
        ]. Although blockchain technologies
initially emerged in the financial sector, their transformative potential has been recognised across
various domains beyond cryptocurrencies. In addition to their foundational role in the financial
industry, including applications in decentralised finance and lending, blockchain technologies are
increasingly being leveraged in areas such as supply chains and logistics, healthcare, and governance
[
        <xref ref-type="bibr" rid="ref1 ref3 ref4 ref5">1, 3, 4, 5</xref>
        ]. Software developers in these domains are increasingly adopting blockchain technologies
because of their fundamental properties, such as decentralisation, immutability, and transparency,
which collectively enhance security, ensure data integrity, and support automated processes [
        <xref ref-type="bibr" rid="ref1 ref6 ref7">1, 6, 7</xref>
        ].
      </p>
      <p>
        One of fundamental characteristic of blockchain is decentralisation. Decentralization creates an
environment in which all participants equally contribute to creating and managing records and
collectively hold ownership of them. In blockchain networks, each participant keeps a copy of the records
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Complete data transparency is inherently achieved because all participants maintain a complete
copy of the records. Efective data sharing among participants relies on the immutability of all records,
making it a core feature of these systems [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. Immutability means that data can only be written to
and read from the blockchain. Unlike traditional databases, operations such as modifying or deleting
data are not supported. Decentralisation, immutability, and transparency are the cornerstones for
establishing trust among participants in blockchain systems, eliminating the need for a trusted third
party [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]. These properties ensure that no single party controls the data, that records cannot be altered,
and that all transactions are visible and verifiable by all stakeholders. The elimination of the need for a
central authority paves the way for innovation in electronic commerce and enables more eficient data
exchange between organisations.
      </p>
      <p>CEUR</p>
      <p>ceur-ws.org</p>
      <p>
        Blockchain technologies would have limited practical value without their programmability, which
enables the development of custom applications and the integration of solutions into existing information
systems [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. The key component enabling blockchain programmability is the smart contracts. The
rapid expansion and widespread adoption of blockchain technology have positioned smart contracts
as a fundamental component of secure and automated digital transactions. Smart contracts, often
described as self-executing agreements, run directly on blockchain networks, eliminating the need for
intermediaries and enhancing transparency [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ].
      </p>
      <p>
        On one hand, these features ofer various advantages to businesses. On the other hand, they
increase the complexity of verifying the correctness of applications that incorporate them, particularly
the correctness, reliability, security, and expected behaviour of applications [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. For the successful
integration of blockchain technologies into enterprise software solutions, it is essential to manage and
efectively verify the quality of the developed applications throughout the development process. Given
the relative novelty of these technologies, there is a lack of established guidelines for implementing an
efective quality assurance process. Due to the specific characteristics of blockchain systems, generic
software engineering approaches are often inadequate, and quality assurance processes must be tailored
accordingly [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. Among these characteristics, immutability is a fundamental property that significantly
impacts the design, development, and verification of blockchain-based applications. Identifying an
efective quality evaluation process is the central focus of this research.
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. Background</title>
      <sec id="sec-2-1">
        <title>2.1. The architecture of decentralised applications</title>
        <p>
          A central component that enables the programmability of blockchains is undoubtedly smart contracts.
Smart contracts typically do not function as standalone applications, but they serve as the core
component of decentralised applications (DApps). They contain solely the program logic, implementing
both the business logic and the access of smart contracts to data [
          <xref ref-type="bibr" rid="ref10">10</xref>
          ]. Decentralised applications are
true applications in the complete sense of the word, as they encapsulate smart contracts and expose
their functionalities externally, usually through a graphical user interface or an API. Decentralised
applications consist of two main components: (1) a front-end, usually implemented as a web application
using HTML, CSS, and JavaScript, and (2) a back-end, which includes smart contracts typically written
in Solidity or other related languages such as Vyper, or Rust [
          <xref ref-type="bibr" rid="ref11">11</xref>
          ]. It is important to emphasise that the
architecture presented serves as a generic reference model for decentralised applications and that, in
enterprise settings, data are rarely stored exclusively on the blockchain. Instead, organisations typically
adopt hybrid storage strategies that combine blockchain storage with additional databases, such as
relational or document-oriented databases, to manage and persist data more eficiently.
        </p>
        <p>
          On the outside, decentralised applications are somewhat like web applications [
          <xref ref-type="bibr" rid="ref11">11</xref>
          ]. However, their
internal architecture is significantly more complex. The front-end with the user interface and the
back-end with smart contracts are separate and independent components communicating through
message exchanges. While its deployment location does not restrict the front-end of a decentralised
application, smart contracts must run within virtual machines on the nodes of the blockchain network.
        </p>
        <p>
          Smart contracts are executed in the isolated environment of blockchain networks. As the core
component enabling programmability, they inherit immutability, a fundamental property of blockchain
technology [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ]. In practice, immutability means that smart contracts cannot be easily modified or
upgraded once deployed. However, the ability to change, upgrade, and maintain software is one of the
fundamental attributes of internal software quality. As such, the immutability of smart contracts poses
a significant challenge to established and well-practised approaches in software development, including
software quality assessment [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ].
        </p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Validation and verification</title>
        <p>Verification and validation are core processes for ensuring quality, both using testing for achieving
set quality goals [14]. The aim of the processes is to support and assist in building quality into the
system during the product life cycle [15]. While validation focuses on checking if the developed item
corresponds to stakeholders’ needs, verification discovers if the item is developed in a proper way,
following specifications, specified requirements, and other documents [ 16].</p>
        <p>When employing static and dynamic testing approaches, validation and verification is supported [ 14].
Static testing evaluate test item without execution, while dynamic testing involve exciting source code
for the testing purposes [14]. Static testing range from reviews, model verification and static analysis,
while, on the other hand, dynamic testing includes specification-, structured-, and experience-based
approaches [14].</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Related work</title>
      <p>This research presents a review of literature reviews in the quality assessment of applications based on
blockchain technologies. As part of the review, we systematically analysed and synthesised existing
secondary research that addresses such applications’ validation, verification, or testing. Following a
preliminary literature review, we did not find any tertiary literature reviews that directly address the
ifeld of quality assessment of blockchain applications. However, the broader literature review revealed
several related tertiary studies that generally address validation and verification in software engineering.
We identified two related tertiary studies briefly reviewed below due to their relevance to the software
product quality assessment field.</p>
      <p>Garousi and Mäntylä [17], in their tertiary study, provide a comprehensive overview of the state of
accumulated knowledge on software testing during the period from 1994 to 2015 when the study was
conducted. After the conducted review, the study pool included 101 secondary studies. Their study
aims to systematically map the secondary studies in the field of testing. The research can serve as a
summarising index of relevant testing information that supports evidence-based decision-making in
any given area of software engineering. The research ofers insights into the most frequently addressed
testing methods (e.g. model-based approach, regression testing) and software products that are of most
significant interest within the testing domain.</p>
      <p>In their study, Tran et al. [18] focus on the assessing of the quality of testing artifacts. The main
objective of the study is to develop a comprehensive model for capturing the factors of test case quality,
which are relevant for various perspectives. As part of their literature review, they identified 49 relevant
secondary studies published between 2008 and 2019. Based on a review of secondary literature, the
authors present the factors that describe the diferent contexts in which the quality of test cases is
studied. The authors also provide a comprehensive model for test case quality, which defines the quality
attributes of their measurements, all based on existing research and the international standard ISO/IEC
25010:2011 [19].</p>
    </sec>
    <sec id="sec-4">
      <title>4. Research method</title>
      <p>In designing this review of literature reviews, we follow the methodology for conducting a standard
systematic literature review, following the example of related research in software engineering [ 17, 20].
The study clearly defines the research questions we aim to answer. It outlines the search strategy
for identifying secondary studies and explicitly states the inclusion and exclusion criteria. The study
describes the procedure for selecting relevant secondary studies and the data extraction process. The
continuation of the research focuses on analysing the data collected from secondary studies and
synthesising knowledge in the field of validation and verification of blockchain applications. This
synthesis provides answers to the previously defined research questions.</p>
      <sec id="sec-4-1">
        <title>4.1. Goal of the study</title>
        <p>Since blockchain technologies are relatively novel compared to other software products, the quality
assurance process for such solutions is not yet as well-established as it is in developing conventional
applications, e.g. web or mobile applications. Due to the many specific characteristics of blockchain
technologies, software product validation and verification processes must be adopted and adapted
accordingly. An eficient quality assurance framework is essential for successfully executing IT projects
involving blockchain technologies.</p>
        <p>This study is based on reviewing secondary sources, mainly systematic literature reviews and
systematic mapping studies, aiming to form a comprehensive picture of the risks and available methods
in ensuring the quality of blockchain applications. There are several advantages in using secondary
literature sources instead of primary sources. Firstly, secondary sources summarize and synthesize
knowledge from a larger number of primary studies, which provides more condensed information on
the topic under consideration. The second reason is the systematic nature of the reviews conducted and
the critical evaluation of the sources examined. Topics that recur more frequently can be considered
more important in the field. Lastly, it is necessary to consider the breadth of the field of quality research.
Although blockchain application development is relatively young, it would be dificult to fully address
primary studies given the wide range of quality attributes considered, which the quality assurance
process requires.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Research questions</title>
        <p>Software quality assurance can be approached from two perspectives: (1) the process perspective
(topdown perspective), which focuses on the validation and verification workflow along with appropriate
techniques and methods, and (2) the product-oriented perspective (bottom-up), which addresses specific
quality challenges in the software itself and seeks efective solutions. A common ground between both
perspectives lies in the selection of approaches and methods to ensure the quality of blockchain-based
applications. Therefore, in this study, we examine the field of software verification and validation from
both the process-oriented and the challenge-driven points of view. In line with this approach, we have
formulated the following research questions:
– RQ1: How can we validate and verify blockchain applications?
– RQ2: Which quality attributes of blockchain applications are directly addressed in secondary
studies?</p>
        <p>Research question RQ1 provides approaches and state-of-the-art techniques that can be used during
the development process of blockchain applications to verify and validate quality aspects of blockchain
applications. Within the scope of research question RQ2, we identify challenges in quality attributes of
blockchain-based applications. The research question identified aspects of internal quality of blockchain
applications that require special attention during development process. The frequency of occurrence
of each quality attribute in the secondary sources also suggests the importance of individual quality
aspects.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. Search process</title>
        <p>The search for secondary literature was conducted to identify existing systematic reviews, mapping
studies, and survey articles that address the validation and verification of blockchain applications. The
following search string was used:</p>
        <p>(”smart contract” OR ”blockchain application” OR ”dApps”) AND (”testing” OR ”validation” OR
”verification” OR ”detection”) AND (”review” OR ”mapping” OR ”survey” OR ”research direction”).</p>
        <p>The stated query is written in a generic form. The actual queries were adapted to the specific online
academic libraries used. This query was designed to capture various terms related to blockchain-based
applications, including (1) smart contracts and decentralised applications; (2) quality assurance activities,
such as testing, validation, verification, and detection; and (3) typical descriptors of secondary studies,
such as reviews, mapping studies, and surveys. The literature search was conducted using the following
online academic libraries:
– ScienceDirect (https://www.sciencedirect.com/),
– IEEE Xplore (https://ieeexplore.ieee.org/),
– SpringerLink (https://link.springer.com/),
– Scopus (https://www.elsevier.com/products/scopus),
– ACM Digital Library (https://dl.acm.org/).</p>
        <p>These databases were selected based on their extensive coverage of peer-reviewed publications in
the fields of computer science, software engineering, and emerging technologies, including blockchain.
By combining multiple databases, the search process aimed to maximise the breadth of the collected
literature and reduce the risk of overlooking relevant secondary studies.</p>
      </sec>
      <sec id="sec-4-4">
        <title>4.4. Inclusion and exclusion criteria</title>
        <p>The number of retrieved papers by online academic libraries is reduced by specifying a strict number of
inclusion and exclusion criteria. In the study, only peer-reviewed papers from journal and conferences
are included. Given the relative youth of the blockchain research field, we did not impose any time
restrictions on the search. All sources relevant to the domain were considered. Only English-language
papers were included, including surveys, literature reviews and mapping studies addressing the
validation, verification, or testing of blockchain-based applications. The complete list of adopted inclusion
and exclusion criteria is presented in Table 1.</p>
      </sec>
      <sec id="sec-4-5">
        <title>4.5. Validity threats</title>
        <p>In the following section, we discuss potential threats to the validity of this study.</p>
        <p>The first possible threat to the validity of this research is that it may miss relevant secondary studies
in the field. We mitigated this risk by careful development and evaluation of our search strings. A
related validity threat is caused by our decision to exclude grey literature from the study. The study,
therefore, represents an exclusively academic perspective on the topic under consideration, excluding
industry reports. However, since we reviewed secondary and not primary studies, the risk of excluding
relevant but not peer-reviewed material is low. Since our data extraction in this study is based on
secondary studies, relevant information about verifying and validating blockchain applications available
in primary studies may no longer be available in secondary studies. This thread is inherent to any
review based on secondary studies. We accept this threat as a trade-of for the breadth of the research
domain that can be covered through secondary studies.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Results of the study</title>
      <p>This section presents and elaborates on the study’s results, answering the two research questions
introduced in Section 4.2.</p>
      <sec id="sec-5-1">
        <title>5.1. Overview of selected studies</title>
        <p>The literature search was carried out in June 2025, resulting in 37 unique papers published since 2019.
The formulated search query was executed across a selection of online scientific databases. Table 2
presents the number of papers retrieved from each individual database.</p>
        <p>The initial set of 377 papers retrieved from various online academic libraries was compiled and
reviewed. After screening the titles and abstracts for relevance, 73 papers were selected for further
consideration. Applying the inclusion and exclusion criteria and removing duplicates reduced the set
to 59 unique papers. Finally, after a full-text review, 37 papers were deemed eligible and included in
the study. Table 3 provides a list of the selected literature, along with details on its id, publication year,
type, and source. All identified studies in the table are marked with a unique identifier in the format Sx,
where x represents the sequential number of the study. This identification method was introduced to
enable simpler and more concise referencing throughout the text of the paper.</p>
        <p>Figure 5.1 shows the distribution of selected studies according to their publication year and source.
The relative novelty of the research field focusing on the quality of blockchain-based applications is
evident from the distribution of publications over the years. The earliest publication dates back to
2019, while the highest number of annual publications was recorded in 2024, with 11 papers across the
included online academic libraries. This trend suggests that the field remains of ongoing interest to
researchers. The Figure also shows that the maximum number of publications come from IEEE Xplore.
Only one from ACM Digital Libraries meets our inclusion criteria.</p>
      </sec>
      <sec id="sec-5-2">
        <title>5.2. Process of verification and validation - RQ1</title>
        <p>
          The primary objective of the validation and verification process is to evaluate both the functional
and non-functional aspects of blockchain application quality [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. Among the 37 secondary studies
analysed, 15 address the validation and verification process in techniques in the context of blockchain
applications, representing 41% of the secondary studies included in our review. Studies S3, S9, S11,
S13-17, S20-21, S24, S26, S29, S32, and S36 are particularly relevant to the response to the research
question RV1. Verification and validation, as an overarching process comprehensively addressed within
the development lifecycle of blockchain applications, is specifically discussed in three studies (S3, S9,
and S26). Paper S14 addresses the security assurance of blockchain solutions within the development
lifecycle. Based on the reviewed studies, verification and validation approaches can be grouped into
two main branches: static analysis, which focuses on analysing the source code of smart contracts,
and dynamic analysis, which examines the behavior of the program during execution [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. Static code
analysis is used for examining data and control flow, performing taint analysis, and identifying program
code patterns that represent vulnerability. Pattern analysis is primarily applied in security assessments
and in evaluating gas consumption eficiency.
        </p>
        <p>Within dynamic analysis, we can further distinguish two major categories of techniques: testing
and performance analysis. Performance analysis is less thoroughly discussed in the reviewed studies.
Namely, only study S3 addresses this topic in detail, while sources S24 and S32 merely mention the
techniques and ofer only a brief description.</p>
        <p>Testing represents one of the most prominent groups of verification and validations techniques.
The majority of the studies addressing the validation and verification process focus on testing. Our
review identified 7 sources that discuss testing in the context of blockchain applications. Of these 7
studies, 6 studies (S13, S17, S20, S24, S29, and S32) examine testing in general and present a range
of testing techniques used in primary studies. Among the secondary sources, the most frequently
highlighted techniques are fuzz testing and mutation testing. Fuzz testing is an automated software
testing technique based on injecting large amounts of random (including incorrect) input data into a
program. Its primary purpose is to trigger crashes or unexpected behaviours, which makes it especially
useful for security testing. Another important automated technique is mutation testing, which is not
used for directly testing software products, but rather for evaluating the quality of test cases. The
ScienceDirect</p>
        <p>IEEE</p>
        <p>SpringerLink</p>
        <p>Scopus</p>
        <p>ACM
core idea is to introduce small intentional random changes into the program code, called mutants, and
assess how efectively test suites detect those changes. Testing from the perspective of model-based
development is addressed in more detail by paper S20.</p>
        <p>Other testing techniques, mentioned in review studies, are unit testing, functional testing, integration
testing, model-based testing, security testing, and performance testing, which further includes stress
testing, load testing, and scalability testing. One of the seven identified sources, study S16 focuses
specifically on acceptance testing.</p>
        <p>
          Formal verification represents the next major group of techniques. Most formal techniques are based
on static analysis. However, some also incorporate dynamic approaches, making it dificult to classify
within a single category. A common characteristic of all formal verification techniques is their reliance
on formal proof and mathematical modelling to demonstrate the functional or security compliance of a
software design [
          <xref ref-type="bibr" rid="ref10">10</xref>
          ]. This approach fundamentally difers from testing, which derives quality assurance
through empirical evaluation of the system’s behavior.
        </p>
        <p>The core techniques of formal verification include theorem proving, model checking, and abstract
interpretation. Some of the reviewed studies also consider runtime verification and dynamic symbolic
execution as part of the formal verification domain, although these methods combine elements of
formalism and program execution. Among the reviewed studies, four focus on techniques of the formal
verification, namely S11, S15, S21, and S36. The study S36 highlights verification techniques, with an
exclusive focus on their application to security aspects. The overview and classification of verification
and validation techniques is shown in Figure 2.</p>
      </sec>
      <sec id="sec-5-3">
        <title>5.3. Quality challenges of blockchain applications - RQ2</title>
        <p>The analysis of the collected studies revealed that the majority of contributions included in our review
adopt a bottom-up approach. Among the 37 secondary studies analysed, 22 focus on the quality-related
aspects and attributes of blockchain applications, accounting for 59% of the studies considered in our
review. These studies do not target the overall validation end verification process but rather aim to
provide solutions to concrete quality-related issues. Among the identified secondary studies that follow
the bottom-up approach, some studies that address specific challenges (e.g. vulnerability), the other
focus on individual aspects or quality attributes of blockchain applications (e.g. security). For research
question RV2, studies S1-2, S4-8, S10, S12, S18-19, S22-23, S25, S27-28, S30-31, S33-35, and S37 are
particularly relevant.</p>
        <p>The analysis of challenges addressed by the reviewed studies reveals a certain monotony in the field.
The primary quality related challenge in blockchain applications is related to vulnerabilities in smart
contracts. Analysis reveals that 15 identified studies (S2, S4, S6-8, S12, S18, S23, S25, S27-28, S33-35,
and S37) focus primarily on vulnerability detection and prevention in smart contracts as the central
quality assurance issue. The main objective of these secondary studies is to compile a set of known
vulnerabilities and provide a list of tools that can be used to detect and mitigate them. Vulnerability
detection techniques and tools are mainly based on static code analysis and increasingly leverage
machine learning and deep learning approaches (e.g., S2, S33). Some studies also focus on new static
analysis techniques, the optimization of established formal verification methods, and the advancement
of testing strategies.</p>
        <p>The review also identifies 7 studies (S1, S5, S10, S19, S22, and S30-31) that address the broader topic of
security in blockchain applications. The primary focus of the papers revolves around security analysis
and evaluation. However, it is characteristic of these studies that security is typically framed in terms
of vulnerabilities and their mitigation.</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>6. Discussion</title>
      <p>The immutability of smart contracts is that limitation of blockchain applications that needs to be
adequately addressed during the development process of such applications. Techniques and methods for
evaluating the quality of blockchain applications adhere to the principle of deploying smart contracts
to networks only when they do not contain bugs, vulnerabilities, and other shortcomings. This would
eliminate the need for later corrections to smart contracts.</p>
      <p>The literature review shows a wide spectrum of available techniques. The first important group is
formal verification. Formal verification techniques employ mathematical models and formal proofs to
rigorously demonstrate the functional correctness and security robustness of smart contract designs.
The techniques can therefore be used to mathematically prove that smart contracts function according
to specifications. Formal methods do, however, have limitations. Their use can be limited if the systems
are too complex or it does not have a limited number of states. In such cases, it is sensible to use testing.</p>
      <p>In area of testing blockchain applications, fuzz testing and mutation testing are the most frequently
highlighted techniques. The fuzz testing automates the generation of a large quantity of random
input data, including incorrect inputs, which are passed into smart contracts inputs. This approach
creates circumstances in which edge cases of operation are also tested, which, in addition to functional
incorrectness, also reveals potential vulnerabilities in the program code. The mutation testing technique
represents a validation of applied testing that evaluates its coverage. Small mutations in the program
code must be detected by the test suite, for the testing process to be considered efective. Relevant
approaches for the field include techniques based on static analysis of source code. The purpose of
these techniques is to detect and eliminate problematic code that could lead to vulnerabilities in smart
contracts.</p>
      <p>The literature review suggests that the removal of defects and vulnerabilities in blockchain
applications is a multi-stage process. No single technique can fully address the quality challenges of blockchain
applications. Therefore, they should be used in a complementary manner whenever possible.</p>
      <p>Our analysis of the main quality challenges in developing blockchain applications shows that
secondary studies focus predominantly on security. As thoroughly documented by Wei et al. [45], security
incidents have historically undermined trust in safety of blockchain solutions. The immutability of
smart contracts once deployed, combined with the need to ensure security, significantly increases the
engineering efort required to develop reliable blockchain applications. The reviewed secondary sources
provide a detailed and comprehensive solution of security concerns, ofering numerous vulnerability
detection tools and methods that can be directly applied in practice by developers of blockchain
applications. However, security is only one of several critical quality attributes, and a comprehensive
quality assurance approach must also address other aspects beyond security. In the future, it is expected
that the academic community will devote similar attention to other aspects of the internal quality of
blockchain applications as it currently does to security.</p>
    </sec>
    <sec id="sec-7">
      <title>7. Conclusions</title>
      <p>The development of blockchain applications and their integration into business environments presents
a vital engineering challenge for two main reasons. First, compared to conventional web applications,
blockchain-based applications are architecturally more complex. They contain smart contracts as a key
component. Second, once smart contracts are deployed on a blockchain network, they cannot be easily
replaced with upgraded or fixed versions.</p>
      <p>The primary objective of this systematic review of secondary sources is to examine aggregated
knowledge resources and to identify key specifics in the quality assurance of blockchain applications.
Recognizing these specifics is essential for constructing a comprehensive quality assurance process
tailored to blockchain-based applications.</p>
      <p>A top-down analysis of the secondary literature reveals a wide range of techniques, highlighting
formal verification and static analysis as key approaches that complement traditional testing techniques
for blockchain applications. In contrast, a bottom-up perspective uncovers a relatively modest coverage
of internal quality aspects. Most identified studies focus on the security aspect of smart contracts, while
other quality attributes remain unaddressed in the secondary literature.</p>
      <p>To develop a comprehensive quality assurance process model for blockchain applications, evaluating
the suitability of individual techniques within specific contexts will be necessary. Individual techniques
do not represent universal solutions for quality assessment and should be used complementarily.
Furthermore, quality assurance techniques for other internal quality attributes of blockchain applications
must be explored. Based on the findings of this review, the area of internal quality attributes presents
numerous opportunities for future research.</p>
      <p>Based on identified secondary sources in the validation and verification of blockchain applications,
the article lays the foundation for further research to conduct an in-depth analysis of validation and
verification techniques. Future work will focus on identifying novel techniques and adapting existing
ones in the domain, as well as exploring the application of composite approaches for validating and
verifying blockchain applications. A significant challenge for future studies will be including sources
beyond the academic community, such as industry reports and white papers.</p>
    </sec>
    <sec id="sec-8">
      <title>Acknowledgments</title>
      <p>The authors acknowledge financial support from the Slovenian Research and Innovation Agency
(Research Core Funding No. P2-0057).</p>
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      <title>Declaration on Generative AI</title>
      <p>During the preparation of this work, the authors used ChatGPT, Gemini, and Grammarly for grammar
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