You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Software Testing Process Models Benefits&Drawbacks: a Systematic Literature Review 
Chapter Title:  Background 
1. Abstract of Cited Paper (BIB001):  Software testing process is an activity, in which the software is verified to comply with the requirements and validated to operate as intended. As software development adopts new development methods, this means also that the test processes need to be changed. In this qualitative study, we observe ten software organizations to understand how organizations develop their test processes and how they adopt new test methods. Based on our observations, organizations do only sporadic test process development, and are conservative when adopting new ideas or testing methods. Organizations need to have a clear concept of what to develop and how to implement the needed changes before they commit to process development. 
2. Abstract of Cited Paper (BIB002):  One of the latest additions in defining the test process is the upcoming ISO/IEC 29119 standard, which aims to define a universally applicable generic test process model. However, currently the standard does not offer any support for the adoption process of the model. In this paper, we present our framework, which aims to combine a maturity level-based approach with the standard process. Our objective was to create an easy-to-use framework for organizations to assess how closely their existing test process follows the standard, and give feedback on improvement objectives. Our results indicate that combining maturity levels with the standard is a viable approach to assess the implementation of the standard in practice. 
3. Abstract of Cited Paper (BIB003):  Model-based testing (MBT) provides a systematic and automated way to facilitate rigorous testing of software systems. MBT has been an intense area of research and a large number of MBT techniques have been developed in the literature and in the practice. However, all of the techniques have been developed using their own concepts and terminology of MBT, which are very often different than other techniques and at times have conflicting semantics. Moreover, while working on MBT projects with our industrial partners in the last several years, we were unable to find a unified way of defining MBT techniques based on standard terminology. To precisely define MBT concepts with the aim of providing common understanding of MBT terminology across techniques, we formalize a small subset of the recently released ISO/IEC/IEEE 29119 Software Testing Standard as a conceptual model (UML class diagrams) together with OCL constraints. The conceptual model captures all the necessary concepts based on the standard terminology that are mandatory or optional in the context of MBT techniques and can be used to define new MBT tools and techniques. To validate the conceptual model, we instantiated its concepts for various MBT techniques previously developed in the context of our industrial partners. Such instantiation automatically enforces the specified OCL constraints. This type of validation provided us feedback to further refine the conceptual model. Finally, we also provide our experiences and lessons learnt for such formalization and validation.

Literature Review:
Software testing is an important phase of software development. IEEE definition  suggests that "software testing is the process of exercising or evaluating a system by manual or automatic means to verify that it satisfies specified requirements or to identify differences between actual and expected results". Software testing is crucial as it involves critical activities from unit, integration, system, to acceptance testing BIB001 . Following indications from testing models / standards and best practices, it is essential to improve the overall testing process. Nevertheless, there are still many organizations that do not follow best practices and perform testing in an ad-hoc way  BIB002 . For the purpose of facilitating and improving testing in organizations, several test models have been designed since the '80s  . The aim of the models is to develop structured and systematic testing processes based on organizational needs. In literature, there are different terms used when addressing formalization of testing processes, such as testing frameworks, testing improvement processes, testing models, testing standards, with the following definitions: • The term testing framework is more often used in the sense of specific tools and practices applied for tests creation  . • Software testing models and test improvement processes are commonly used interchangeably. However, according to Veenendaal  , two types of models are distinguished for test process improvement: test improvement models (also called test maturity models) and content-based models. -The core of test improvement models consists of testing best practices with the structure divided into several maturity levels  . -Content-based models describe different testing practices in detail without pre-defined paths for the improvement process in the form of different maturity levels  . According to the ISO/IEC/IEEE 24765:2017(E) standard  , models and standards are defined as follows: • a model is the "representation of a real-world process, device, or concept"  ; • a standard is a "document, established by consensus and approved by a recognized body, that provides, for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context"  . In this paper, we focus on the whole set of testing models, including both categories: test maturity models and content-based models. We also include testing standards (e.g. ISO/IEC/IEEE 29119 BIB004 BIB003 ), as they are testing models backed by standards development organizations like IEEE, IEC, and ISO. From this point, when we refer to testing models, we include test improvement models, contentbased models and testing standards.