PyTest Installation and pytest identifies the test files and test methods in PyTest

How to install PyTest

To install the latest version of pytest, execute the following command.

Pip install pytest

Confirm the installation using the following command to display the help section of pytest.

Pytest -h

How pytest identifies the test files and test methods

pytest only identifies the file names starting with test_ or ending with _test as the test files in the current directory and subdirectories. Pytest automatically identifies those files as test files. We can make pytest run other filenames by explicitly mentioning them.

Pytest requires the test function names to start with test. Function names which are not of format test* are not considered as test functions by pytest. We cannot explicitly make pytest consider any function not starting with test as a test function.

some examples of valid and invalid pytest file names

test_add.py – valid

subtract_test.py – valid

testadd.py – invalid

subtracttest.py – invalid

login.py --- invalid

some examples of valid and invalid pytest test methods

def test_addition() – valid

def testaddition() – valid

def addition() – invalid 

Note: Even if we explicitly mention addition() pytest will not run this method. 

Basic PyTest Example

Create a new directory named pytestautomation and navigate into the directory in your command line.

Create a file named test_addition.py and add the below code to that file. 

import pytest

def test_add():
    assert (10+5 ==15)

def testaddeven_num():
    assert(4+4==9)

 Run the test using below command in command line

Note: you should navigate  into the directory in your command line. 

c:\pytest 

output will be

F says failure

Dot(.) says success. 

In the failures section, you can see the failed method and the line of failure. Here 4+4 == 9 which is false. 

In the end, we can see test execution summary, 1 failed and 1 passed.

Now, I want to result more explanatory about the test , you can use below command in command line 

C:\Pytest -v 

Output will be

Note : pytest command will execute all the files of format test_* or *_test in the current directory and subdirectories.

Run tests by node ids
Each collected test is assigned a unique nodeid which consist of the module filename followed by:: characters
To run a specific test within a module:
Pytest test_addition.py::test_add

Output Will be