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How to correctly write preconditions in test cases

  • 13.01.2021
  • Posted by: Admin
How to write preconditions in test case

In today’s «QA tips for newbies» rubric, we’re going to talk about how to compose test cases correctly.

Test Case – is a set of steps, specific conditions and parameters which are necessary for the verification of tested functionality of its part.

Preconditions – is a list of necessary preparatory actions (application settings, testing environment settings) for execution on the current test case.

Preconditions contain important information/acts which are needed for the prior preparation of the operating system, application, mobile device, browser etc. Preparation of these conditions should always come before test cases execution. Without meeting the requirements, mentioned in preconditions, the test case either will not be passed or the results will not be correct.

Preconditions can consist of one or several sentences. There are no certain restrictions of sentences count in preconditions but it’s preferable to limit its size by several lines. Same as steps, preconditions should contain minimum requirement (but sufficient) information amount.

Also, preconditions can be designed as steps if it’s justified by a specific situation (e.g. its necessary for correct preparation).

Preconditions are not a required test case attribute. They can be left unfilled if they are unnecessary. But, during passing our courses preconditions are necessary for any test case.

For example

Incorrect variant Correct variant
Incorrect variant

The user is authorized through the «Authorization» form on the main page and located on personal account page
Note:
The overly detailed description is used here

Correct variant

The user is authorized and located on personal account page
Incorrect variant

There is more than 1 item in the cart 

Note:

Here there is the lack of important information about authorization. This could be important, for example, when the purchases of goods are expected and the user should be authorized. Otherwise, the additional information input will be needed.
Correct variant

The user is authorized. There is more than 1 item in the cart
Incorrect variant

Preconditions are empty

Note:

In this case preconditions are required, because if the PATH to application libraries isn’t described, the application will not work correctly.
Correct variant

The PATH to application libraries is described in the Operating System settings

If we have several test cases, in each of which we should perform several steps, and these steps aren't objects of testing, then we can (for all the same type test cases) design them as preconditions.

For example, we have to create 2 test cases for the «My address» tab verification.

Using preconditions, we could write test cases shorter and more convenient to perceive:

Test case №1 (without preconditions) Test case №1 (with preconditions)
Test case №1 (without preconditions)

Preconditions: —

  1. Authorize on the site
  2. Click the «Settings» button
  3. Choose the «Personal account» option from the dropdown
  4. Choose the «My address» tab in the personal account 
  5. Fill all text fields with valid data
  6. Click the «Save» button
  7. Click the «Edit» button
  8. Change the entered data
  9. Click the «Save» button
Test case №1 (with preconditions)

Preconditions:

The user is authorized on the site and located on the «My Address» tab of the  personal account page 

  1. Fill all the text fields with valid data
  2. Click the «Save» button
  3. Click the «Edit» button
  4. Change the entered data
  5. Click the «Save» button
Test case №2 (without preconditions) Test case №2 (with preconditions)
Test case №2 (without preconditions)

Preconditions: —

  1. Authorize on site
  2. Click the «Settings» button
  3. Choose the «Personal account» option from the dropdown
  4. Choose the «My address» tab in the personal account 
  5. Fill all text fields with valid data
  6. Click the «Save» button
  7. Click the «Edit» button
  8. Change the entered data
  9. Click the «Cancel» button
Test case №2 (with preconditions)

Preconditions:

The user is authorized on the site and located in the «My Address» tab of the personal account page

  1. Fill all text fields with valid data
  2. Click the «Save» button
  3. Click the «Edit» button
  4. Change the entered data
  5. Click the «Cancel» button

This way, through the use of the  preconditions, we have reduced the amount of steps of every test case for at least 4 steps . The understanding of these test cases has not become worse, but it significantly reduced the size of them.

We recommend our students to look closely at this information, because it will be one of the reference points during homework checking and evaluation.

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