functions 2

Since I know how to use variables, I can do better with the results of test_why_use_a_function

open the project

  • I change directory to the functions folder

    cd functions

    the terminal shows I am in the functions folder

    .../pumping_python/functions (main)

  • I use pytest-watcher to run the tests

    uv run pytest-watcher . --now

    the terminal shows

    rootdir: .../pumping_python/functions
configfile: pyproject.toml
collected 12 items

tests/test_functions.py ............                          [100%]

======================= 12 passed in X.YZs =========================

  • I hold ctrl on the keyboard and click on tests/test_functions.py to open it in the editor

a better way to handle the results changing

RED: make it fail

  • I add 2 variables to test_why_use_a_function

     7    def test_why_use_a_function(self):
 8        def add_x(x=3, y=0):
 9            return x + y
10
11        x = 3
12        y = 0
13        self.assertEqual(add_x(y=0), 3)

  • I use the variables in the assertion

    11        x = 3
12        y = 0
13        # self.assertEqual(add_x(y=0), 3)
14        self.assertEqual(add_x(x, y), x+x)
15        self.assertEqual(add_x(y=1), 4)

    the terminal shows AssertionError

    AssertionError: 3 != 6

GREEN: make it pass

I change the expectation

14          x = 3
15          y = 0
16          # self.assertEqual(add_x(y=0), 3)
17          self.assertEqual(add_x(x, y), x+y)
18          self.assertEqual(add_x(y=1), 4)

the test passes

REFACTOR: make it better

  • I remove the comment then do the same thing for the next assertion

    11        x = 3
12        y = 0
13        self.assertEqual(add_x(x, y), x+y)
14        y = 1
15        # self.assertEqual(add_x(y=1), 4)
16        self.assertEqual(add_x(x, y), x+x)
17        self.assertEqual(add_x(y=2), 5)

    the terminal shows AssertionError

    AssertionError: 4 != 6

  • I change the expectation

    14        y = 1
15        # self.assertEqual(add_x(y=1), 4)
16        self.assertEqual(add_x(x, y), x+y)
17        self.assertEqual(add_x(y=2), 5)

    the test passes. Wait a minute, self.assertEqual(add_x(x, y), x+y) is also a repetition!

  • I remove the comment then add a variable for the next assertion

    14        y = 1
15        self.assertEqual(add_x(x, y), x+y)
16        y = 2
17        # self.assertEqual(add_x(y=2), 5)
18        self.assertEqual(add_x(x, y), y+y)
19        self.assertEqual(add_x(y=3), 6)

    the terminal shows AssertionError

    AssertionError: 5 != 4

  • I change the expectation to the right calculation

    16        y = 2
17        # self.assertEqual(add_x(y=2), 5)
18        self.assertEqual(add_x(x, y), x+y)
19        self.assertEqual(add_x(y=3), 6)

    the test passes, this is the same as the add function from how to make a calculator

  • I remove the comment, then add a variable for the next assertion

    16        y = 2
17        self.assertEqual(add_x(x, y), x+y)
18        y = 3
19        # self.assertEqual(add_x(y=3), 6)
20        self.assertEqual(add_x(x, y), x+y)
21        self.assertEqual(add_x(y=4), 7)

    the test is still green because x and y are both 3

  • on to the next one

    18        y = 3
19        self.assertEqual(add_x(x, y), x+y)
20        y = 4
21        # self.assertEqual(add_x(y=4), 7)
22        self.assertEqual(add_x(x, y), y+y)
23        self.assertEqual(add_x(y=5), 8)

    the terminal shows AssertionError

    AssertionError: 7 != 8

  • I change the expectation

    20        y = 4
21        # self.assertEqual(add_x(y=4), 7)
22        self.assertEqual(add_x(x, y), x+y)
23        self.assertEqual(add_x(y=5), 8)

    the test passes

  • I remove the comment, then add a variable

    20        y = 4
21        self.assertEqual(add_x(x, y), x+y)
22        y = 5
23        # self.assertEqual(add_x(y=5), 8)
24        self.assertEqual(add_x(x, x), x+y)
25        self.assertEqual(add_x(y=6), 9)

    the terminal shows AssertionError

    AssertionError: 6 != 8

  • I change the call

    22        y = 5
23        # self.assertEqual(add_x(y=5), 8)
24        self.assertEqual(add_x(x, y), x+y)
25        self.assertEqual(add_x(y=6), 9)

    the test passes

  • I remove the comment then add a variable

    22        y = 5
23        self.assertEqual(add_x(x, y), x+y)
24        y = 6
25        # self.assertEqual(add_x(y=6), 9)
26        self.assertEqual(add_x(y, y), x+y)
27        self.assertEqual(add_x(y=7), 10)

    the terminal shows AssertionError

    AssertionError: 12 != 9

  • I change the call

    24        y = 6
25        # self.assertEqual(add_x(y=6), 9)
26        self.assertEqual(add_x(x, y), x+y)
27        self.assertEqual(add_x(y=7), 10)

    the test passes

  • I remove the comment then add a variable

    24        y = 6
25        self.assertEqual(add_x(x, y), x+y)
26        y = 7
27        # self.assertEqual(add_x(y=7), 10)
28        self.assertEqual(add_x(x, y), y+y)
29        self.assertEqual(add_x(y=8), 11)

    the terminal shows AssertionError

    AssertionError: 10 != 14

  • I change the expectation

    26        y = 7
27        # self.assertEqual(add_x(y=7), 10)
28        self.assertEqual(add_x(x, y), x+y)
29        self.assertEqual(add_x(y=8), 11)

    the test passes

  • I remove the comment then add one more variable

    26        y = 7
27        self.assertEqual(add_x(x, y), x+y)
28        y = 8
29        # self.assertEqual(add_x(y=8), 11)
30        self.assertEqual(add_x(x, y), x+x)

    the terminal shows AssertionError

    AssertionError: 11 != 6

  • I change the expectation

    26        y = 8
27        # self.assertEqual(add_x(y=8), 11)
28        self.assertEqual(add_x(x, y), x+y)

    the test passes

  • I remove the comment then use the Rename Symbol feature to change the name of the add_x function to add

     7    def test_why_use_a_function(self):
 8        def add(x=3, y=0):
 9            return x + y
10
11        x = 4
12        y = 0
13        self.assertEqual(add(x, y), x+y)
14        y = 1
15        self.assertEqual(add(x, y), x+y)
16        y = 2
17        self.assertEqual(add(x, y), x+y)
18        y = 3
19        self.assertEqual(add(x, y), x+y)
20        y = 4
21        self.assertEqual(add(x, y), x+y)
22        y = 5
23        self.assertEqual(add(x, y), x+y)
24        y = 6
25        self.assertEqual(add(x, y), x+y)
26        y = 7
27        self.assertEqual(add(x, y), x+y)
28        y = 8
29        self.assertEqual(add(x, y), x+y)
30
31    def test_making_a_function_w_pass(self):

  • I only have to make a change in one place if I want to test what happens when I add 4 to a number. I change x

     7    def test_why_use_a_function(self):
 8        def add(x=3, y=0):
 9            return x + y
10
11        x = 4
12        y = 0
13        self.assertEqual(add(x, y), x+y)

    the test is still green

  • I only have to make a change in one place if I want to test what happens when I add 5 to a number. I change x

     7    def test_why_use_a_function(self):
 8        def add(x=3, y=0):
 9            return x + y
10
11        x = 5
12        y = 0
13        self.assertEqual(add_x(x, y), x+y)

    still green.

  • I only have to make a change in one place if I want to test what happens when I add 6 to a number. I change x

     7    def test_why_use_a_function(self):
 8        def add(x=3, y=0):
 9            return x + y
10
11        x = 6
12        y = 0
13        self.assertEqual(add_x(x, y), x+y)

    green. Much better than what I had before, the test passes for any number I try, but there has to be a better way that does not need all these lines of code

I can use a variable to remove duplication

close the project

  • I close test_functions.py and functions.py in the editor

  • I click in the terminal and use q on the keyboard to leave the tests and the terminal goes back to the command line

  • I change directory to the parent of functions

    cd ..

    the terminal shows

    .../pumping_python

    I am back in the pumping_python directory

review

I ran tests to show that I can make functions with

as a reminder

How many questions can you answer about functions?

code from the chapter

Do you want to see all the CODE I typed in this chapter?

what is next?

you know

There is a problem, I have done these same steps for each of the chapters up till now

I think I know how to make a Python Test Driven Development environment. I am going to write a program that will do all the steps for making a project for me, so I never have to do those steps again.

Would you like to know how to make a Python Test Driven Development environment automatically?

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