Comparing values (equality, inequality) in PyTest

Introduction

We compare values to check if things are the same or different. This helps us find mistakes in our code.

Check if a function returns the expected result.

Verify that two variables hold the same value after some operation.

Ensure that an error message is not equal to an empty string.

Confirm that a list length is not equal to zero after adding items.

Test if user input matches the required format or value.

Syntax

PyTest

assert actual == expected  # checks if values are equal
assert actual != unexpected  # checks if values are not equal

Use == to check if two values are exactly the same.

Use != to check if two values are different.

Examples

This test passes because 5 is equal to 5.

PyTest

def test_equal():
    assert 5 == 5

This test passes because 5 is not equal to 3.

PyTest

def test_not_equal():
    assert 5 != 3

Checks if two strings are the same.

PyTest

def test_string_equal():
    assert 'hello' == 'hello'

Checks if two strings are different.

PyTest

def test_string_not_equal():
    assert 'hello' != 'world'

Sample Program

This sample has two tests. The first checks if adding 2 and 3 equals 5. The second checks that adding 2 and 2 does not equal 5.

PyTest

import pytest

def add(a, b):
    return a + b

def test_add_equal():
    result = add(2, 3)
    assert result == 5

def test_add_not_equal():
    result = add(2, 2)
    assert result != 5

Important Notes

Always use assert in pytest to compare values.

Clear and simple comparisons help find bugs quickly.

Use meaningful variable names to make tests easy to read.

Summary

Use == to check if values are equal.

Use != to check if values are not equal.

Assertions help confirm your code works as expected.