How to Assert Dictionary Equality in pytest: Simple Guide

In pytest, you can assert that two dictionaries are equal using the simple assert dict1 == dict2 statement. Pytest will automatically compare keys and values and show differences if the assertion fails.

Syntax

Use the assert keyword followed by the equality check between two dictionaries. Pytest handles the comparison and reports detailed differences if they are not equal.

• dict1: The first dictionary to compare.
• dict2: The second dictionary to compare.
• ==: Checks if both dictionaries have the same keys and corresponding values.

python

assert dict1 == dict2

Example

This example shows how to write a pytest test function that asserts two dictionaries are equal. If they differ, pytest will show which keys or values do not match.

python

def test_dict_equality():
    expected = {"name": "Alice", "age": 30, "city": "Paris"}
    actual = {"name": "Alice", "age": 30, "city": "Paris"}
    assert actual == expected

Output

============================= test session starts ==============================
collected 1 item

test_sample.py .                                                          [100%]

============================== 1 passed in 0.01s ===============================

Common Pitfalls

Common mistakes include:

• Using assert dict1 is dict2 which checks identity, not equality.
• Comparing dictionaries with different key types or missing keys.
• Ignoring nested dictionaries where deep equality is needed.

Always use == for value equality, not is.

python

def test_wrong_assert():
    dict1 = {"a": 1}
    dict2 = {"a": 1}
    # Wrong: checks if both are the same object (will fail)
    # assert dict1 is dict2
    # Right: checks if contents are equal
    assert dict1 == dict2

Quick Reference

Action	Code Example	Description
Check dict equality	assert dict1 == dict2	Passes if both dicts have same keys and values
Check dict identity (not recommended)	assert dict1 is dict2	Checks if both variables point to same object
Compare nested dicts	assert dict1 == dict2	Works if nested dicts have same structure and values

Key Takeaways

Use assert dict1 == dict2 to check dictionary equality in pytest.

Avoid using 'is' for dictionary comparison as it checks object identity, not content.

Pytest shows detailed differences when dictionary assertions fail.

Ensure nested dictionaries are structured the same for equality to pass.

Simple assert statements are enough; no extra pytest functions needed.