What is Test Case and Test Model?

Question

Software testing

Hey! I delve into the general theory of testing, I settled on the concept of a test case and a test model.
1) As I understand it, there is no exact definition of the term, but can one simply explain in a human way what all such includes a test case?
2) A test model and a test plan are completely different things?

Answer 1

1) A test case is one, very specific scenario for testing a certain functionality. A coherent test case usually includes not only the actual action to be performed and the expected behavior of the system, but also, at a minimum, the necessary conditions and the subsequent state.
Let me explain with an example. Toaster has functionality that allows you to use some HTML tags in the response and comment text. A test case for this functionality might look (simplified) like this:
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ID : UI1234
Author : V. Pupkin
Category : UI, manual, validation
Description : HTML tags in the response body
Precondition : Server is running and available, The list contains at least one question, user is logged in
Steps : Select a question from the list. In the response field, type the text in which we use [list] and other HTML tags, and then click the "Submit" button.
Expected : Entered text is displayed in full, HTML tags [allowed] are displayed resp. markup, all other tags are ignored.
Postcondition : The server is still available, the number of questions in the list has not changed, there has not been a fire in the data center, etc.
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Accordingly, if during the test execution something was not executed (the markup was not displayed, the data center burned down, or the answer was written without authorization - no matter what), the test is considered failed.
This is, so to speak, the most illustrative example for the case of manual testing. But the same is true for unit tests, load tests, etc. The bottom line is that testing is not a random "poking anywhere", but a meaningful, purposeful check of the system's performance, and a test case is one, completely specific stage of this check.
2) A test model is a model of the system functionality and / or user behavior that allows you to automatically generate test cases. (This can't be explained clearly in a few words.)
Well, the test plan is generally from another opera. This is a document that describes in detail and thoroughly which parts of the system, how (and why exactly) we test, what it gives us (and what it does not) and justifies why this approach provides the required product quality. It is usually compiled jointly by the architect / tech lead and the responsible QA during the development process.