MDO1988 where did you find that the .setdefault() is faster? i tested it on my pc and i found .get() as faster.

if the key doesn't exist d.setdefault() will insert it with the default value. We don't need/want this behavior for this Kata, therefore d.get() is a better choice here ^^

No, the tests are ok, there is no such test, the test is like this:

Test.assert_equals(expression_matter(1, 3, 1), 5)

Click reset if you see otherwise.

You're welcome, closing the question.

Compare your result with the expected result:

'1 * 5 = 5 \n2 * 5 = 10 \n3 * 5 = 15 \n4 * 5 = 20 \n5 * 5 = 25 \n6 * 5 = 30 \n7 * 5 = 35 \n8 * 5 = 40 \n9 * 5 = 45 \n10 * 5 = 50' should equal 
'1 * 5 = 5\n2 * 5 = 10\n3 * 5 = 15\n4 * 5 = 20\n5 * 5 = 25\n6 * 5 = 30\n7 * 5 = 35\n8 * 5 = 40\n9 * 5 = 45\n10 * 5 = 50'

You have some extra spaces.

First of all, thank you for following those instructions, you've done that right.

print returns None, remove it from your code, return the string.