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Integration testing (sometimes called integration and testing, abbreviated I&T) is the phase in software testing in which individual software modules are combined and tested as a group. Integration testing is conducted to evaluate the compliance of a system or component with specified functional requirements.
A mixed integration testing follows a combination of top down and bottom-up testing approaches. In top-down approach, testing can start only after the top-level module have been coded and unit tested. In bottom-up approach, testing can start only after the bottom level modules are ready
In Top Down Integration testing approach the main module is designed at first then the submodules/subroutines are called from it. In Bottom Up Integration testing approach different modulesare created first then these modules are integrated with the main function. ... The complexity of this testing is simple.

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Mercy P... Integration testing
1. Top Down Integration Testing :
Top Down Integration testing which is also known as Incremental integration testing. In this Top Down approach the higher level modules are tested first after higher level modules the lower level modules are tested. Then these modules undergo for integration accordingly. Here the higher level modules refers to main module and lower level modules refers to submodules. This approach uses Stubs which are mainly used to simulate the submodule, if the invoked submodule is not developed this Stub works as a momentary replacement.

2. Bottom Up Integration Testing :
Bottom Up Integration testing is another approach of Integration testing. In this Bottom Up approach the lower level modules are tested first after lower level modules the higher level modules are tested. Then these modules undergo for integration accordingly. Here the lower level modules refers to submodules and higher level modules refers to main modules. This approach uses test drivers which are mainly used to initiate and pass the required data to the sub modules means from higher level module to lower level module if required.

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Integration testing type focuses on testing interfaces that are “implicit
and explicit” and “internal and external”.

Top down:
Integration testing involves testing the topmost component interface with other components from top to bottom.
If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

Bottom down:
Integration testing involves testing the topmost component interface with other components from top to bottom.
If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

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INTEGRATION TESTING :
A system is made up of multiple components or modules which comprises hardware and software. Integration is defined as the set of interaction among modules. Testing the interaction between modules and interaction with other systems externally is called integration testing. The final round of integration involving all components is called Final Integration Testing (FTT), or system integration.
Integration testing is both a phase and a type of testing. The architecture and design gives details of interactions within systems. Testing the interactions between one system and another system requires detailed understanding  of how they work together. This knowledge of integration depends on many modules and systems. To reduce the complexity within modules, a phase in testing is dedicated to test the interactions , this is called integration testing phase.
Top-down integration:
* Integration testing involves testing the topmost component interface with other components from top to bottom.
* If a set of components and their related interfaces can deliver functionality without expecting presence of other components or minimal interface requirement in software / product, then the set of components and their related interfaces are called “sub-system”.
* Each sub-system works independently.
* It makes integration testing easier and enables focus on required interfaces.
* If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.
Bottom – up integration:
* In Bottom – up integration, the components for a new product development available in reverse order, starting from the bottom.
* The arrows from top-bottom indicate interaction or control flow.
* The arrows from bottom-top indicate integration approach or integration path.
* The following steps are performed in bottom-up integration:
• Low-level components are combined as Clusters.
• A driver is written to coordinate test case input and output.
• The cluster is tested.
• Drivers are removed and clusters are combined moving upward in program structure.

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In this section, we are going to discuss the difference between top-down and bottom-up integration testing; and see a brief introduction of them.
Top down integration::
In top-down incremental integration testing, we will add the modules incrementally or one by one and test the data flow in similar order as we can see in the below diagram:

This testing technique deals with how higher-level modules are tested with lower-level modules until all the modules have been tested successfully.

In the top-down method, we will also make sure that the module we are adding is the child of the previous one, like Child C, is a child of Child B.

The purpose of executing top-down integration testing is to detect the significant design flaws and fix them early because required modules are tested first.

Buttom up integration::

This type of testing method deals with how lower-level modules are tested with higher-level modules until all the modules have been tested successfully.

In bottom-up testing, the top-level critical modules are tested, at last. Hence it may cause a defect.

In simple words, we can say that we will be adding the modules from the bottom to the top and test the data flow in similar order as we can see in the below image:

In the bottom-up method, we will ensure that the modules we are adding are the parent of the previous one as we observe in the following image:

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Top-down integration
Integration testing involves testing the topmost component interface with other components from top to bottom.
Each subsystem works independently.
If a component at a higher-level requires a modification, module is added to bottom, and for each component integration testing needsto be repeated.

Bottom - up integration
The components for a new product development available in reverse order, starting from the bottom.
The arrows from top-bottom indicate interaction or control flow.
The arrows from bottom-top indicate integration approach or integration path.

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Top to Down Integration:
Integration testing involves testing the topmost component interface with other components from top to bottom.
Each sub-system works independently.
If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

Bottom to Up Integration:
In Bottom – up integration, the components for a new product development available in reverse order, starting from the bottom.
The arrows from top-bottom indicate interaction or control flow.
The arrows from bottom-top indicate integration approach or integration path.
The following steps are performed in bottom-up integration:
Low-level components are combined as Clusters.
A driver is written to coordinate test case input and output.
The cluster is tested.
Drivers are removed and clusters are combined moving upward in program structure.

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Integration Testing is a division of software testing that tests interfaces between different software components. Any software module will work well individually, but when it’s integrated with a different module, there are chances where the software might not behave as intended.

Top-down Integration Testing

In this approach, testing is performed from the top-most module in the architecture. The testing control flow moves to the bottom from the top. This method will use stubs as duplicate programs to restore the working of modules that are missing. This method is comparatively easier than the bottom-up approach as it uses stubs, which are generally easier to write than the drivers.

Bottom-up  Integration Testing

Here the testing starts from the lowest module in the architecture. The testing control flow moves upwards from the bottom. This method will be executed whenever the top modules are under development. This method will use the drivers to restore the working of modules that are missing. This way of approach has a high success ratio and is an efficient way to test and develop a product. It is faster than the other traditional methods of testing.

Dhivyadhashini.k

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Top-down Integration Testing

It is also known as incremental integration testing.

The higher level modules are first tested after which the lower level modules are tested.

Once it is done, they are integrated.

The higher level modules are the main modules and the lower level modules are the submodules.

It uses stubs to simulate the sub-modules.

If the sub-module hasn’t been fully developed, the stub acts like a replacement to it.

It is useful in cases where significant defect occurs at the top of the program.

The main module is designed first and then the submodules or subroutines are called from it.

It is implemented on structure or procedure-oriented programming languages.It is a simple testing technique.

It works on big to small components.

Stub modules need to be produced.

Bottom-up Integration Testing :

The lower level modules are tested first after which the higher level modules are tested.

The lower level modules are the sub-modules and higher level modules are the main modules.

It uses test drivers to initiate and pass the required data to the sub-modules.

The test drivers are used to simulate the main module.

If the main module hasn’t been developed yet, the driver works as a replacement to it.

It is useful in cases where the crucial flaws are identified at the bottom of the program.

It is generally implemented on object-oriented programming languages.

It is highly complex and data intensive.
It works on small to big components.

The driver modules need to be produced.

# data[].attributes.body
Integration testing is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

# data[].attributes.body
Top-down integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated.In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

# data[].attributes.body
Integration testing
It is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

Bottom-Up Integration Testing
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

Top-Down Integration Testing
Top-down integration testing technique used in order to simulate the behavior of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

# data[].attributes.body
Integration testing:
It is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

💫 Bottom-Up Integration Testing :
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

💫 Top-Down Integration Testing :
Top-down integration testing technique used in order to simulate the behavior of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the System is working as intended

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INTEGRATION TESTING
A system is made up of multiple components or modules which comprises hardware and software. Integration is defined as the set of interaction among modules. Testing the interaction between modules and interaction with other systems externally is called integration testing. The final round of integration involving all components is called Final Integration Testing (FTT), or system integration.
Integration testing is both a phase and a type of testing. The architecture and design gives details of interactions within systems. Testing the interactions between one system and another system requires detailed understanding  of how they work together. This knowledge of integration depends on many modules and systems. To reduce the complexity within modules, a phase in testing is dedicated to test the interactions , this is called integration testing phase.
Top-down integration: *Integration testing involves testing the topmost component interface with other components from top to bottom.
* If a set of components and their related interfaces can deliver functionality without expecting presence of other components or minimal interface requirement in software / product, then the set of components and their related interfaces are called “sub-system”.
* Each sub-system works independently.
*It makes integration testing easier and enables focus on required interfaces.
*If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.
Bottom – up integration:
* In Bottom – up integration, the components for a new product development available in reverse order, starting from the bottom.
* The arrows from top-bottom indicate interaction or control flow.
* The arrows from bottom-top indicate integration approach or integration path.
* The following steps are performed in bottom-up integration:
• Low-level components are combined as Clusters.
• A driver is written to coordinate test case input and output.
• The cluster is tested.
• Drivers are removed and clusters are combined moving upward in program structure.

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INTEGRATION TESTING-(Top Down & Bottom Up):-

# data[].attributes.subject
INTEGRATION TESTING-(Top Down & Bottom Up):-

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Integration Testing:-
Integration testing is a type of testing meant to check the combinations of different units, their interactions, the way subsystems unite into one common system, and code compliance with the requirements.

Top Down:-
🔹Top Down Integration testing which is also known as Incremental integration testing.
🔹In this Top Down approach the higher level modules are tested first after higher level modules the lower level modules are tested.
🔹Then these modules undergo for integration accordingly. Here the higher level modules refers to main module and lower level modules refers to submodules.
🔹This approach uses Stubs which are mainly used to simulate the submodule, if the invoked submodule is not developed this Stub works as a momentary replacement.

Bottom Up:-
🔹Bottom Up Integration testing is another approach of Integration testing.
🔹In this Bottom Up approach the lower level modules are tested first after lower level modules the higher level modules are tested.
🔹Then these modules undergo for integration accordingly. Here the lower level modules refers to submodules and higher level modules refers to main modules.
🔹This approach uses test drivers which are mainly used to initiate and pass the required data to the sub modules means from higher level module to lower level module if required.
-Manju Bharkavi P

# data[].attributes.body
INTEGRATION TESTING is defined as a type of testing where software modules are integrated logically and tested as a group. A typical software project consists of multiple software modules, coded by different programmers.

Top-Down Integration Testing:
Top-down integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated.In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

Bottom-Up Integration Testing:
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

# data[].attributes.body
Integration Testing is a division of software testing that tests interfaces between different software components. Any software module will work well individually, but when it’s integrated with a different module, there are chances where the software might not behave as intended.

Top-Down Integration Testing
Top-down integration testing technique used in order to simulate the behavior of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

Bottom-Up Integration Testing
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

# data[].attributes.headline
Aishwarya.J                              Top-down integration

# data[].attributes.subject
Aishwarya.J                              Top-down integration

# data[].attributes.body
•Integration testing involves testing the top most component interface with other component from top to bottom
•If a set of components and their related interfaces without expecting set of components and their related interface are called sub system
•Each sub system works independently
•If a higher level modification, module is added to bottom and for each component integration testing needs to be repeated.

Bottom -up integration
•In bottom up integration the components for a new product development available in reverse order,starting from the bottom
•The arrows from top-bottom indicate interaction or control flow
•The arrows from bottom-up indicate integration approach or integration path.
•Low level components are combined as clusters
•A driven is written to coordinate test case input and output
•The clusters is tested
•Driven are removed and clusters are combined moving upward in program structure .

# data[].attributes.body
INTEGRATION TESTING
A system is made up of multiple components or modules which comprises hardware and software. Integration is defined as the set of interaction among modules. Testing the interaction between modules and interaction with other systems externally is called integration testing. The final round of integration involving all components is called Final Integration Testing (FTT), or system integration.
Integration testing is both a phase and a type of testing. The architecture and design gives details of interactions within systems. Testing the interactions between one system and another system requires detailed understanding  of how they work together. This knowledge of integration depends on many modules and systems. To reduce the complexity within modules, a phase in testing is dedicated to test the interactions , this is called integration testing phase.
Top-down integration: *Integration testing involves testing the topmost component interface with other components from top to bottom.
* If a set of components and their related interfaces can deliver functionality without expecting presence of other components or minimal interface requirement in software / product, then the set of components and their related interfaces are called “sub-system”.
* Each sub-system works independently.
*It makes integration testing easier and enables focus on required interfaces.
*If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.
Bottom – up integration:
* In Bottom – up integration, the components for a new product development available in reverse order, starting from the bottom.
* The arrows from top-bottom indicate interaction or control flow.
* The arrows from bottom-top indicate integration approach or integration path.
* The following steps are performed in bottom-up integration:
• Low-level components are combined as Clusters.
• A driver is written to coordinate test case input and output.
• The cluster is tested.
• Drivers are removed and clusters are combined moving upward in program structure.

# data[].attributes.body
Integration Testing:
•It is the process of testing the interface between the two software units or module.
•It focuses on determining the correctness of the interface

Bottom-up integration testing:
•In bottom -up testing ,each module at lower level is tested with higher modules untill all modules are tested.
•The primary purpose of this integration testing is,each subsystems is to test the interface among various modules making up the subsystem.
•This integration testing uses test drivers to drive and pass appropriate data to the lower modules.
Advantages:
*no stubs are required.
*several disjoint subsystems can be tested simultaneously.
Dis advantages:
*driver modules must be produced.
*the complexity that occurs when the system is made up of large number of small subsystems.

Top -down integration testing:
•Top down integration testing technique used in order to simulate the behaviour of the lower level modules that are not yet integrated.
testing takes place from top to bottom.
•First high level modules are tested and then low level modules and finally integrating the low level modules to high level modules to ensure the system is working as intended.
Advantages:
*separately dubbing modules.
*few or no drivers needed.
*it is more stable and accurate at the aggregate level.
Dis advantages:
*needs many stubs.
*modules at lower levels are tested inadequately.

# data[].attributes.body
Integration testing
Integration testing
It is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

Bottom-Up Integration Testing
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

Top-Down Integration Testing
Top-down integration testing technique used in order to simulate the behavior of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level

# data[].attributes.body
Bottom-Up Integration Testing –

In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

Advantages:

1.In bottom-up testing, no stubs are required.
2.A principle advantage of this integration testing is that several disjoint subsystems can be tested simultaneously.

Disadvantages:

1.Driver modules must be produced.
2.In this testing, the complexity that occurs when the system is made up of a large number of small subsystem.

Top-Down Integration Testing –

Top-down integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated.In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

Advantages:

1.Separately debugged module.
2.Few or no drivers needed.
3.It is more stable and accurate at the aggregate level.

Disadvantages:

1.Needs many Stubs.
2.Modules at lower level are tested inadequately.

# data[].attributes.body
Integration Testing is used to check the data flow between the two modules mostly System is made up of multiple components or modules that can comprise hardware and software.In Integration their is lot of interaction among components so we need to test the interaction between the modules and with other systems externally.Integration testing starts when two modules are available and ends when all component interface have been tested.

Integration testing means testing the interface between modules.They are two types of interface:

Internal interface

External interface

Internal Interface - It provide a communication across two  modules within project or product.

External Interface -It visible to the third party developers and solution providers.

By using Application programming interfaces we can achieve interfaces.API enable one module to call another module it will be external or internal.

Integration Testing type focuses on testing interfaces that are implicit and explicit and internal and external.

Explicit interface are documented were implicit interface are not documented.

There are several methodologies available for integration testing.They are as follows:

Top-down integration

Bottom-up integration

Bi-directional integration

System integration

# data[].attributes.body
Top-down Integration Testing

It is also known as incremental integration testing.

The higher level modules are first tested after which the lower level modules are tested.

Once it is done, they are integrated.

The higher level modules are the main modules and the lower level modules are the submodules.

It uses stubs to simulate the sub-modules.

If the sub-module hasn’t been fully developed, the stub acts like a replacement to it.

It is useful in cases where significant defect occurs at the top of the program.

The main module is designed first and then the submodules or subroutines are called from it.

It is implemented on structure or procedure-oriented programming languages.

It is a simple testing technique.

It works on big to small components.

Stub modules need to be produced

Bottom-up Integration Testing

The lower level modules are tested first after which the higher level modules are tested.

The lower level modules are the sub-modules and higher level modules are the main modules.

It uses test drivers to initiate and pass the required data to the sub-modules.

The test drivers are used to simulate the main module.

If the main module hasn’t been developed yet, the driver works as a replacement to it.

It is useful in cases where the crucial flaws are identified at the bottom of the program.

It is generally implemented on object-oriented programming languages.

It is highly complex and data intensive.

It works on small to big components.

The driver modules need to be produced.

# data[].attributes.body
Integration testing type focuses on testing interfaces that are “implicit
and explicit” and “internal and external”.

Top down:
Integration testing involves testing the topmost component interface with other components from top to bottom.
If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

Bottom down:
Integration testing involves testing the topmost component interface with other components from top to bottom.
If a component at a higher – level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

# data[].attributes.body
Integration Testing:
•It is the process of testing the interface between the two software units or module.
•It focuses on determining the correctness of the interface

Bottom-up integration testing:
•In bottom -up testing ,each module at lower level is tested with higher modules untill all modules are tested.
•The primary purpose of this integration testing is,each subsystems is to test the interface among various modules making up the subsystem.
•This integration testing uses test drivers to drive and pass appropriate data to the lower modules.
Advantages:
*no stubs are required.
*several disjoint subsystems can be tested simultaneously.
Dis advantages:
*driver modules must be produced.
*the complexity that occurs when the system is made up of large number of small subsystems.

Top -down integration testing:
•Top down integration testing technique used in order to simulate the behaviour of the lower level modules that are not yet integrated.
testing takes place from top to bottom.
•First high level modules are tested and then low level modules and finally integrating the low level modules to high level modules to ensure the system is working as intended.
Advantages:
*separately dubbing modules.
*few or no drivers needed.
*it is more stable and accurate at the aggregate level.
Dis advantages:
*needs many stubs.
*modules at lower levels are tested inadequately.

# data[].attributes.body
Integration Testing:
•It is the process of testing the interface between the two software units or module.
•It focuses on determining the correctness of the interface

Top-down integration

Integration testing involves testing the topmost component interface with other components from top to bottom.

Each subsystem works independently.

If a component at a higher-level requires a modification, module is added to bottom, and for each component integration testing needs to be repeated.

Bottom - up integration

The components for a new product development available in reverse order, starting from the bottom.

The arrows from top-bottom indicate interaction or control flow.

The arrows from bottom-top indicate integration approach or integration path.

# data[].attributes.body
Integration Testing

Integration testing is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

Top to Down Integration Testing –
Top-down integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

Bottom-Up Integration Testing –

In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

# data[].attributes.body
Integration testing is the process of testing the interface between two software units or module. It’s focus on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

Top-Down Integration Testing –
Top-down integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated. In this integration testing, testing takes place from top to bottom. First high-level modules are tested and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended.

Advantages:

Separately debugged module.

Few or no drivers needed.

It is more stable and accurate at the aggregate level.

Bottom-Up Integration Testing –
In bottom-up testing, each module at lower levels is tested with higher modules until all modules are tested. The primary purpose of this integration testing is, each subsystem is to test the interfaces among various modules making up the subsystem. This integration testing uses test drivers to drive and pass appropriate data to the lower level modules.

Advantages:

In bottom-up testing, no stubs are required.

A principle advantage of this integration testing is that several disjoint subsystems can be tested simultaneously.

# data[].attributes.body
Integration testing is the second level of the software testing process comes after unit testing. In this testing, units or individual components of the software are tested in a group. The focus of the integration testing level is to expose defects at the time of interaction between integrated components or units.

TOP-DOWN TESTING:
The top-down testing strategy deals with the process in which higher level modules are tested with lower level modules until the successful completion of testing of all the modules. Major design flaws can be detected and fixed early because critical modules tested first. In this type of method, we will add the modules incrementally or one by one and check the data flow in the same order.

In the top-down approach, we will be ensuring that the module we are adding is the child of the previous one like Child C is a child of Child B

Bottom-Up Method:

The bottom to up testing strategy deals with the process in which lower level modules are tested with higher level modules until the successful completion of testing of all the modules. Top level critical modules are tested at last, so it may cause a defect. Or we can say that we will be adding the modules from bottom to the top and check the data flow in the same order.

In the bottom-up method, we will ensure that the modules we are adding are the parent of the previous one