Type of Testing

1) Functional Testing

2) Non-Functional Testing

3) Maintenance

What is Functional Testing?
This type of testing is used to check the functionality of an application according to the requirement documents, we will mostly prefer FRS (functional requirement specification) to understand the functionality.
for example, if we check the login and registration module of an application then it is called functional testing.
it will be divided into different modules,sub-module, components.
90% automation testing of application is based on functional testing.
What is NON-Functional Testing?
This type of testing is based on non-functional requirements such as security, performance, accessibility, load, and volume. 
this testing always will be performed parallel with functional testing or  after the completion of functional testing
Check the Performance of an application online.

We mostly prefer automation tools to check nonfunctional testing.

Apache JMeter, Load Runner, TestNG
https://gtmetrix.com
What is maintenance?
This type of testing will be applied after the successful deployment of an application. if the client will change the requirement or the client is not satisfied with development after deployment then the maintenance phase will work.
this testing will be performed after the re-development of an application. regression testing is the best example of maintenance.

Type of testing or approach:-

1 Black Box Testing:-

this type of testing will be used to check functionality using Form -elements and multiple page elements, it will check the application using UI(user interface).it is also called external layer testing.

no need to evaluate the source code of an application, we can perform a testing operation using the external layer of an application.
if we check the functionality using a manual testing process then we mostly prefer black-box testing.
it can be done by the customer, client, or manual tester because code awareness is not required in black-box testing.
it is called Black-box because the code will be hidden, we can check the application using UI(User Interface).
2 White Box Testing:-
it will be done by the development team because coding knowledge is required. Manual Testers have no role in white-box testing, it is basically used to verify the program code of the application by the SR. Programmer or Project lead. They will also check code standards, comments, help, and code execution time.

In the case of white-box testing, developers also check extra code and code optimization, design pattern, project architecture flow, etc.

Whitebox testing will be implemented by the Sr. development team, they will check the code standard of developers.

3 Gray box:-

It is a combination of black-box and white-box testing means the development team and testing team will work together in case of gray-box testing.

It can be implemented after the completion of white-box testing and black-box testing to review the bug of its.

in the Agile model, the gray box testing type will be preferred.

Type of Functional Testing:-
...............................................................................................................

Function Testing has multiple types but we are discussing some important types.
Note:-  all types of testing will not be used only a particular testing type will be used according to test plan documents.

1 Alpha testing:-
This testing will be performed under the internal testing team or development in the company. The in-house team of the company will test the application in alpha testing, all types of testing can be executed in alpha testing according to test plan documents. Alpha testing follows complete STLC to test the project.

It will be implemented before the release of the actual software.

2 Beta Testing:-
This type of testing will be performed by end-users to provide reviews and bugs of the live project.
mostly product-based software released under the beta version to get customer reviews and bugs in the live implementation. you can see and operate many beta versions of software in the IT industry.

3 Gamma Testing:-
It will be always performed after the completion of beta testing and check all reviews and bugs of beta testing which have been resolved by the development team or not.
it is the last stage of testing because it will be performed before the release of the actual version of the software.
4 Unit Testing:- 
This type of testing will be implemented by the developer to cross-check program code, method execution of particular components of an application from another section of an application.
It will always perform during the development of the project to check all functions of a class in OOP'S pattern and particular method in a procedural pattern.
for example, if we create a simple interest calculation-based program in the project then we check that the SI method accepts valid input and display accurate output with a different type of input combination is managed by Unit testing.
It will reduce testing time and no need to do other types of testing because unit testing provides 80% project quality and check the internal functionality.

let's discuss the example of unit testing in Python code

Developer side

def addition(a,b):

    try:

      print(a+b)

    except:

       print("Invalid Data") 

tester side

import unittesting

unittesting.addition("abcv","xyz")

unittesting.addition(10,2)

unittesting.addition(10,2.2)

class Add

{

   int c;

   void addition(int a, int b)

   {

    try

    {

     c = a+b;

     System.out.println(c);

    }

    catch(Exception ex)

    {

        System.out.println(ex.getMessage());

    } 

   }

}

import java.util.Scanner;

class Addmain

{

  public static void main(String args[])

{

try

{

  Scanner sc = new Scanner(System.in);

System.out.println("Enter First Number");

int a = sc.nextInt();

System.out.println("Enter Second Number");

int b = sc.nextInt();

 Add obj = new Add();

 obj.addition(a,b); 

}

catch(Exception ex)

{

    System.out.println("Invalid data");

}

}

}

Click these links for the type of testing also
https://shivaconceptsolution.blogspot.com/2019/09/recovery-testing.html
https://shivaconceptsolution.blogspot.com/2019/09/compatibility-testing.html
https://shivaconceptsolution.blogspot.com/2019/09/smoke-and-sanity-testing.html
https://shivaconceptsolution.blogspot.com/2019/09/integration-testing.html