Comparing values (equality, inequality) in PyTest - Build an Automation Script

Verify equality and inequality comparisons between two values

Preconditions (2)

Step 1: Create a test function named test_compare_values

Step 2: Inside the function, define two variables: a = 10 and b = 20

Step 3: Assert that a is not equal to b

Step 4: Assert that a is less than b

Step 5: Assert that b is greater than a

Step 6: Define another variable c = 10

Step 7: Assert that a is equal to c

✅ Expected Result: All assertions pass without errors, confirming correct equality and inequality comparisons.

Automation Requirements - pytest

Assertions Needed:

assert a != b

assert a < b

assert b > a

assert a == c

Best Practices:

Use descriptive test function names

Keep assertions simple and clear

Avoid hardcoding values multiple times by using variables

Run tests with pytest command line for clear output

Automated Solution

PyTest

import pytest

def test_compare_values():
    a = 10
    b = 20
    c = 10

    assert a != b, f"Expected {a} to not equal {b}"
    assert a < b, f"Expected {a} to be less than {b}"
    assert b > a, f"Expected {b} to be greater than {a}"
    assert a == c, f"Expected {a} to equal {c}"

This test function test_compare_values defines three variables a, b, and c with values 10, 20, and 10 respectively.

It then uses assert statements to check:

• Equality: a == c confirms both have the same value.
• Inequality: a != b confirms they differ.
• Less than and greater than: a < b and b > a confirm the relative order.

Each assertion includes a message to help understand failure if it occurs.

Running this with pytest will show a pass if all conditions hold true.

Common Mistakes - 3 Pitfalls

{'mistake': "Using assignment operator '=' instead of equality '==' in assertions", 'why_bad': "This causes syntax errors or unintended behavior because '=' assigns values, it does not compare.", 'correct_approach': "Always use '==' to compare values for equality in assertions."}

Not providing assertion messages

Comparing variables without initializing them

Bonus Challenge

Now add data-driven testing with 3 different pairs of values to compare equality and inequality.

Show Hint

Practice

1. Which operator in pytest assertions checks if two values are equal?

easy

A. <

B. !=

C. >

D. ==

Solution

1. Step 1: Understand equality operator

   The operator == is used to check if two values are equal in Python and pytest assertions.

2. Step 2: Differentiate from inequality

   The operator != checks if values are not equal, so it is not the correct choice for equality.

3. Final Answer:

   == -> Option D

4. Quick Check:

   Equality check = == [OK]

Hint: Use == for equality, != for inequality [OK]

Common Mistakes:

• Confusing == with !=
• Using > or < for equality
• Forgetting to use assertion keyword

2. Which of the following is the correct syntax to assert that variable a is not equal to b in pytest?

easy

A. assert a != b

B. assert a =! b

C. assert a ==! b

D. assert a = b

Solution

1. Step 1: Identify correct inequality syntax

   The correct operator for inequality is !=, so the assertion should be assert a != b.

2. Step 2: Check syntax correctness

   Options with =! or ==! are invalid syntax and will cause errors.

3. Final Answer:

   assert a != b -> Option A

4. Quick Check:

   Inequality assertion = assert a != b [OK]

Hint: Remember: inequality is !=, not =! or ==! [OK]

Common Mistakes:

• Using =! instead of !=
• Using = instead of ==
• Mixing equality and inequality operators

3. What will be the result of this pytest assertion?

def test_numbers():
    x = 10
    y = 5 + 5
    assert x == y

medium

A. Syntax error in assertion

B. Test fails because 10 does not equal 5

C. Test passes because 10 equals 10

D. Test fails because variables are different

Solution

1. Step 1: Calculate values of variables

   Variable x is 10, and y is calculated as 5 + 5, which equals 10.

2. Step 2: Evaluate assertion condition

   The assertion assert x == y checks if 10 equals 10, which is true, so the test passes.

3. Final Answer:

   Test passes because 10 equals 10 -> Option C

4. Quick Check:

   10 == 10 is True [OK]

Hint: Add values before comparing for equality [OK]

Common Mistakes:

• Assuming variables differ without calculation
• Confusing syntax errors with logic errors
• Ignoring that 5 + 5 equals 10

4. Identify the error in this pytest assertion:

def test_strings():
    s1 = "hello"
    s2 = "Hello"
    assert s1 != s2

medium

A. No error, test passes because strings differ in case

B. Syntax error due to missing parentheses

C. Assertion should use == instead of !=

D. Variables s1 and s2 are not defined

Solution

1. Step 1: Compare string values with case sensitivity

   Strings "hello" and "Hello" differ in case, so they are not equal.

2. Step 2: Check assertion correctness

   The assertion assert s1 != s2 correctly checks that the strings are not equal, so the test passes without error.

3. Final Answer:

   No error, test passes because strings differ in case -> Option A

4. Quick Check:

   "hello" != "Hello" is True [OK]

Hint: String comparison is case-sensitive by default [OK]

Common Mistakes:

• Assuming strings are equal ignoring case
• Expecting syntax error without parentheses in assert
• Confusing == and != in assertions

5. You want to write a pytest test to check that a function get_status() returns a value that is not equal to None. Which assertion is the best choice?

hard

A. assert get_status() == None

B. assert get_status() is not None

C. assert get_status() != None

D. assert get_status() is None

Solution

1. Step 1: Understand None comparison best practice

   In Python, to check if a value is not None, the recommended way is to use is not None rather than != None.

2. Step 2: Evaluate options for correctness

   assert get_status() == None checks equality to None (wrong for this case). assert get_status() != None uses != None (works but not best practice). assert get_status() is not None uses is not None which is best practice. assert get_status() is None checks if value is None (opposite of requirement).

3. Final Answer:

   assert get_status() is not None -> Option B

4. Quick Check:

   Use 'is not None' for None checks [OK]

Hint: Use 'is not None' to check for non-None values [OK]

Common Mistakes:

• Using == None instead of is None
• Using != None instead of is not None
• Confusing equality with identity for None