telephone

Part of `Computer Programming`_ is sending input data to a process and getting output data back

input_data -> process -> output_data

I send things (input data) to a program_ to test it, and check if what I think will happen (my expectation) is the same as the results I get (reality). This helps me answer two questions:

  • what is the same?

  • what is different?

The difference helps me know what to change to get what I want. I do this with the assertEqual method, which takes 2 inputs and checks if they are the same

self.assertEqual(reality, my_expectation)

where

  • reality is what happens when I do something with code

  • my_expectation is what I think will happen when I do something with code

The exercises in this chapter show how I can pass input data from a test to a function in a module.

preview

I have these tests by the end of the chapter

start the project

  • I name this project telephone

  • I open a terminal_

  • I use uv_ to make a directory_ for the project and initialize it

    uv init telephone

    the terminal_ shows

    Initialized project `telephone`
at `.../pumping_python/telephone`

    then goes back to the command line.

  • I change directory_ to the project

    cd telephone

    the terminal_ shows I am in the telephone folder_

    .../pumping_python/telephone

  • I make a directory_ for the source code

    mkdir src

    the terminal_ goes back to the command line.

  • I use the `mv program`_ to change the name of main.py to telephone.py and move it to the src folder_

    mv main.py src/telephone.py

    Move-Item main.py src/telephone.py

    the terminal_ goes back to the command line.

  • I `make a directory`_ for the tests

    mkdir tests

    the terminal_ goes back to the command line.

  • I make the tests directory_ a `Python package`_

    Danger

    use 2 underscores (__) before and after init for __init__.py not _init_.py

    touch tests/__init__.py

    New-Item tests/__init__.py

    the terminal_ goes back to the command line.

  • I make a Python file for the tests in the tests directory_

    touch tests/test_telephone.py

    New-Item tests/test_telephone.py

    the terminal_ goes back to the command line.

  • I open test_telephone.py in the editor of the `Integrated Development Environment (IDE)`_

    Tip

    I can open a file_ from the terminal_ in the `Integrated Development Environment (IDE)`_ with the name of the program_ and the name of the file_. That means if I type this in the terminal_

    code tests/test_telephone.py

    `Visual Studio Code`_ opens test_telephone.py in the editor

  • I add the first failing test to test_telephone.py

    1import unittest
2
3
4class TestTelephone(unittest.TestCase):
5
6    def test_failure(self):
7        self.assertFalse(True)

  • I go back to the terminal_ to make a requirements file_ for the `Python packages`_ I need

    echo "pytest" > requirements.txt

    the terminal_ goes back to the command line.

  • I add `pytest-watcher`_ to the requirements file_

    echo "pytest-watcher" >> requirements.txt

    the terminal_ goes back to the command line.

  • I install the `Python packages`_ that I wrote in the requirements file_

    uv add --requirement requirements.txt

    the terminal_ shows that it installed the `Python packages`_

  • I add the new files_ and folders_ to git_ for tracking

    git add .

    the terminal_ goes back to the command line.

  • I add a git_ commit message

    git commit --all --message 'setup project'

    the terminal_ shows

    [main (root-commit) a0b12c3] setup project
 9 files changed, 148 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 .python-version
 create mode 100644 README.md
 create mode 100644 pyproject.toml
 create mode 100644 requirements.txt
 create mode 100644 src/telephone.py
 create mode 100644 tests/__init__.py
 create mode 100644 tests/test_telephone.py
 create mode 100644 uv.lock

    then goes back to the command line.

  • I use `pytest-watcher`_ to run the tests automatically

    uv run pytest-watcher . --now

    the terminal_ is my friend, and shows AssertionError

    ================================ FAILURES ================================
______________________ TestTelephone.test_failure ________________________

self = <tests.test_telephone.TestTelephone testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_telephone.py:7: AssertionError
======================== short test summary info =========================
FAILED tests/test_telephone.py::TestTelephone::test_failure - AssertionError: True is not false
=========================== 1 failed in X.YZs ============================

    because True is NOT False

    if the terminal_ does not show the same error, then check

    • if your tests/__init__.py has two underscores (__) before and after init for __init__.py not _init_.py

    • if you ran echo "pytest-watcher" >> requirements.txt, to add pytest-watcher to the requirements file_

    fix those errors and try to run uv run pytest-watcher . --now again

  • I add AssertionError to the list of Exceptions seen in test_telephone.py in the editor

     4class TestTelephone(unittest.TestCase):
 5
 6    def test_failure(self):
 7        self.assertFalse(True)
 8
 9
10# Exceptions seen
11# AssertionError

  • then I change True to False in the assertion

    7        self.assertFalse(False)

    the test passes.

test_passing_a_string

I can pass a string_ from a test to a function

RED: make it fail

I change test_failure to test_passing_a_string

 4class TestTelephone(unittest.TestCase):
 5
 6    def test_passing_a_string(self):
 7        reality = src.telephone.text('hello')
 8        my_expectation = 'I got: hello'
 9        self.assertEqual(reality, my_expectation)
10
11
12# Exceptions seen
13# AssertionError

the terminal_ is my friend, and shows NameError

NameError: name 'src' is not defined

because there is no definition for src in test_telephone.py

GREEN: make it pass

  • I add NameError to the list of Exceptions seen

    12# Exceptions seen
13# AssertionError
14# NameError

  • I add an `import statement`_ for the telephone module from the src folder_, at the top of the file_

    1import src.telephone
2import unittest
3
4
5class TestTelephone(unittest.TestCase):

  • I add AttributeError to the list of Exceptions seen in test_telephone.py

    13# Exceptions seen
14# AssertionError
15# NameError
16# AttributeError

  • I use the Explorer to open telephone.py from the src folder in the editor

  • I delete the text, then add a name to telephone.py

    1text

    the terminal_ is my friend, and shows NameError

    NameError: name 'text' is not defined

    because the name is in the file_, and I have not told Python_ what it means

  • I point text to None

    1# text
2text = None

    the terminal_ is my friend, and shows TypeError

    TypeError: 'NoneType' object is not callable

    because I cannot call None like a function

  • I add TypeError to the list of Exceptions seen in test_telephone.py

    13# Exceptions seen
14# AssertionError
15# NameError
16# AttributeError
17# TypeError

  • I change text to a function in telephone.py to make it callable_

    1# text
2# text = None
3def text():
4    return None

    the terminal_ is my friend, and shows TypeError

    TypeError: text() takes 0 positional arguments
           but 1 was given

    because the definition for src.telephone.text does not allow calling it with inputs and the test sends 'hello' as input (the parentheses are empty).

  • I make the function take input

    1# text
2# text = None
3# def text():
4def text(the_input):
5    return None

    • the_input is the name I used for the input, I can use any name I want.

    • the terminal_ is my friend, and shows AssertionError

      AssertionError: None != 'I got: hello'

      because the assertion expects 'I got: hello' and the text function returns None.

  • I copy the string_ from the terminal_ and paste it in the `return statement`_ to replace None

    1# text
2# text = None
3# def text():
4def text(the_input):
5    # return None
6    return 'I got: hello'

    the test passes!

REFACTOR: make it better

The problem with this solution is that the text function does not care about what it gets, it always returns 'I got: hello' when called. I want it to return the value it gets as part of the message.

  • I add a new assertion to test_passing_a_string in test_telephone.py

     7    def test_passing_a_string(self):
 8        reality = src.telephone.text('hello')
 9        my_expectation = 'I got: hello'
10        self.assertEqual(reality, my_expectation)
11
12        reality = src.telephone.text('yes')
13        my_expectation = 'I got: yes'
14        self.assertEqual(reality, my_expectation)
15
16
17# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: hello' != 'I got: yes'

    because the text function always returns 'I got: hello' and this assertion expects 'I got: yes'

  • I change the `return statement`_ in telephone.py to match

    1# text
2# text = None
3# def text():
4def text(the_input):
5    # return None
6    # return 'I got: hello'
7    return 'I got: yes'

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: yes' != 'I got: hello'

    it did not work, my change broke the assertion that was passing before. The `return statement`_ has to use the input it gets as part of the output.

what is string interpolation?

  • I use an f-string which lets me add any variables I want to a string_

    1# text
2# text = None
3# def text():
4def text(the_input):
5    # return None
6    # return 'I got: hello'
7    # return 'I got: yes'
8    return f'I got: {the_input}'

    the test passes.

  • I remove the commented lines

    1def text(the_input):
2    return f'I got: {the_input}'

    This is called string interpolation, I can use it to put values in strings_. A string_ is anything inside quotes e.g.

    • 'single quotes'

    • '''triple single quotes'''

    • "double quotes"

    • """triple double quotes"""

  • I add a variable to use the remove repetition of 'hello' from the test in test_telephone.py

     7    def test_passing_a_string(self):
 8        a_string = 'hello'
 9        reality = src.telephone.text('hello')
10        my_expectation = 'I got: hello'
11        self.assertEqual(reality, my_expectation)

  • I use the new variable and string interpolation to remove repetition of 'hello' from the test

     7    def test_passing_a_string(self):
 8        a_string = 'hello'
 9        # reality = src.telephone.text('hello')
10        reality = src.telephone.text(a_string)
11        # my_expectation = 'I got: hello'
12        my_expectation = f'I got: {a_string}'
13        self.assertEqual(reality, my_expectation)

    the test is still green.

  • I add a variable to use to remove repetition of 'yes' from the test

     7    def test_passing_a_string(self):
 8        a_string = 'hello'
 9        # reality = src.telephone.text('hello')
10        reality = src.telephone.text(a_string)
11        # my_expectation = 'I got: hello'
12        my_expectation = f'I got: {a_string}'
13        self.assertEqual(reality, my_expectation)
14
15        a_string = 'yes'
16        reality = src.telephone.text('yes')
17        my_expectation = 'I got: yes'
18        self.assertEqual(reality, my_expectation)

  • I use the new variable and string interpolation to remove repetition of 'yes' from the test

    15        a_string = 'yes'
16        # reality = src.telephone.text('yes')
17        reality = src.telephone.text(a_string)
18        # my_expectation = 'I got: yes'
19        my_expectation = f'I got: {a_string}'
20        self.assertEqual(reality, my_expectation)
21
22
23# Exceptions seen

    still green.

  • I remove the commented lines

     7    def test_passing_a_string(self):
 8        a_string = 'hello'
 9        reality = src.telephone.text(a_string)
10        my_expectation = f'I got: {a_string}'
11        self.assertEqual(reality, my_expectation)
12
13        a_string = 'yes'
14        reality = src.telephone.text(a_string)
15        my_expectation = f'I got: {a_string}'
16        self.assertEqual(reality, my_expectation)
17
18
19# Exceptions seen

  • I open a new terminal_ then change directories to telephone

    cd telephone

    the terminal_ shows I am in the telephone folder_

    .../pumping_python/telephone

  • I add a git_ commit message in the new terminal_

    git commit -am 'add test_passing_a_string'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass a string from a test to a function.

test_passing_none

I can pass None from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a failing test for None (the simplest Python data structure) to test_telephone.py

     7    def test_passing_a_string(self):
 8        a_string = 'hello'
 9        reality = src.telephone.text(a_string)
10        my_expectation = f'I got: {a_string}'
11        self.assertEqual(reality, my_expectation)
12
13        a_string = 'yes'
14        reality = src.telephone.text(a_string)
15        my_expectation = f'I got: {a_string}'
16        self.assertEqual(reality, my_expectation)
17
18    def test_passing_none(self):
19        reality = src.telephone.text(None)
20        my_expectation = 'I got: "None"'
21        self.assertEqual(reality, my_expectation)
22
23
24# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: None' != "I got: 'None'"

GREEN: make it pass

I remove the quotes around None in my_expectation

18    def test_passing_none(self):
19        reality = src.telephone.text(None)
20        # my_expectation = 'I got: "None"'
21        my_expectation = 'I got: None'
22        self.assertEqual(reality, my_expectation)
23
24
25# Exceptions seen

the test passes.

REFACTOR: make it better

  • I remove the comments

    18    def test_passing_none(self):
19        reality = src.telephone.text(None)
20        my_expectation = 'I got: None'
21        self.assertEqual(reality, my_expectation)
22
23
24# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit --all --message 'add test_passing_none'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass None from a test to a function.

test_passing_booleans

I can pass booleans from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for booleans, first with an assertion for False

    18    def test_passing_none(self):
19        reality = src.telephone.text(None)
20        my_expectation = 'I got: None'
21        self.assertEqual(reality, my_expectation)
22
23    def test_passing_booleans(self):
24        reality = src.telephone.text(False)
25        my_expectation = 'I got: "False"'
26        self.assertEqual(reality, my_expectation)
27
28
29# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: False' != 'I got: "False"'

GREEN: make it pass

I remove the quotes around False in my_expectation

23    def test_passing_booleans(self):
24        reality = src.telephone.text(False)
25        # my_expectation = 'I got: "False"'
26        my_expectation = 'I got: False'
27        self.assertEqual(reality, my_expectation)
28
29
30# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add an assertion for True

    23    def test_passing_booleans(self):
24        reality = src.telephone.text(False)
25        my_expectation = 'I got: False'
26        self.assertEqual(reality, my_expectation)
27
28        reality = src.telephone.text(True)
29        my_expectation = 'I got: "True"'
30        self.assertEqual(reality, my_expectation)
31
32
33# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: True' != 'I got: "True"'

  • I remove the quotes around True in my_expectation

    29        reality = src.telephone.text(True)
30        # my_expectation = 'I got: "True"'
31        my_expectation = 'I got: True'
32        self.assertEqual(reality, my_expectation)
33
34
35# Exceptions seen

    the test passes.

  • I remove the comments

    23    def test_passing_booleans(self):
24        reality = src.telephone.text(False)
25        my_expectation = 'I got: False'
26        self.assertEqual(reality, my_expectation)
27
28        reality = src.telephone.text(True)
29        my_expectation = 'I got: True'
30        self.assertEqual(reality, my_expectation)
31
32
33# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit -am 'add test_passing_booleans'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass booleans from a test to a function.

test_passing_an_integer

I can pass an integer_ (a whole number without decimals) from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for an integer_

    28        reality = src.telephone.text(True)
29        my_expectation = 'I got: True'
30        self.assertEqual(reality, my_expectation)
31
32    def test_passing_an_integer(self):
33        reality = src.telephone.text(1234)
34        my_expectation = 'I got: "1234"'
35        self.assertEqual(reality, my_expectation)
36
37
38# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: 1234' != "I got: '1234'"

GREEN: make it pass

I remove the quotes around the integer_ in my_expectation

32    def test_passing_an_integer(self):
33        reality = src.telephone.text(1234)
34        # my_expectation = 'I got: "1234"'
35        my_expectation = 'I got: 1234'
36        self.assertEqual(reality, my_expectation)
37
38
39# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add a variable to use to remove repetition of 1234

    32    def test_passing_an_integer(self):
33        an_integer = 1234
34        reality = src.telephone.text(1234)
35        # my_expectation = 'I got: "1234"'
36        my_expectation = 'I got: 1234'
37        self.assertEqual(reality, my_expectation)
38
39
40# Exceptions seen

  • I use the variable with string interpolation to remove repetition of 1234

    32    def test_passing_an_integer(self):
33        an_integer = 1234
34        # reality = src.telephone.text(1234)
35        reality = src.telephone.text(an_integer)
36        # my_expectation = 'I got: "1234"'
37        # my_expectation = 'I got: 1234'
38        my_expectation = f'I got: {an_integer}'
39        self.assertEqual(reality, my_expectation)
40
41
42# Exceptions seen

    the test is still green.

  • I remove the comments

    32    def test_passing_an_integer(self):
33        an_integer = 1234
34        reality = src.telephone.text(an_integer)
35        my_expectation = f'I got: {an_integer}'
36        self.assertEqual(reality, my_expectation)
37
38
39# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit --all --message \
'add test_passing_an_integer'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass an integer from a test to a function.

test_passing_a_float

I can pass a float_ (binary floating point decimal number) from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for a float_ (binary floating point decimal numbers)

    32    def test_passing_an_integer(self):
33        an_integer = 1234
34        reality = src.telephone.text(an_integer)
35        my_expectation = f'I got: {an_integer}'
36        self.assertEqual(reality, my_expectation)
37
38    def test_passing_a_float(self):
39        reality = src.telephone.text(1.234)
40        my_expectation = 'I got: "1.234"'
41        self.assertEqual(reality, my_expectation)
42
43
44# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: 1.234' != 'I got: "1.234"'

GREEN: make it pass

I remove the quotes around the float_ in my_expectation

38    def test_passing_a_float(self):
39        reality = src.telephone.text(1.234)
40        # my_expectation = 'I got: "1.234"'
41        my_expectation = 'I got: 1.234'
42        self.assertEqual(reality, my_expectation)
43
44
45# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add a variable to use to remove repetition of 1.234

    38    def test_passing_a_float(self):
39      a_float = 1.234
40      reality = src.telephone.text(1.234)
41      # my_expectation = 'I got: "1.234"'
42      my_expectation = 'I got: 1.234'
43      self.assertEqual(reality, my_expectation)
44
45
46# Exceptions seen

  • I use the variable with an f-string to remove repetition of 1.234

    38    def test_passing_a_float(self):
39        a_float = 1.234
40        # reality = src.telephone.text(1.234)
41        reality = src.telephone.text(a_float)
42        # my_expectation = 'I got: "1.234"'
43        # my_expectation = 'I got: 1.234'
44        my_expectation = f'I got: {a_float}'
45        self.assertEqual(reality, my_expectation)
46
47
48# Exceptions seen

    the test is still green.

  • I remove the comments

    38    def test_passing_a_float(self):
39        a_float = 1.234
40        reality = src.telephone.text(a_float)
41        my_expectation = f'I got: {a_float}'
42        self.assertEqual(reality, my_expectation)
43
44
45# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit -am 'add test_passing_a_float'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass a float from a test to a function.

test_passing_a_tuple

I can pass a tuple_ (anything in parentheses ( ) separated by a comma) from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for a tuple_

    38    def test_passing_a_float(self):
39        a_float = 1.234
40        reality = src.telephone.text(a_float)
41        my_expectation = f'I got: {a_float}'
42        self.assertEqual(reality, my_expectation)
43
44    def test_passing_a_tuple(self):
45        reality = src.telephone.text((1, 2, 3, 'n'))
46        my_expectation = 'I got: (1, 2, 3, n)'
47        self.assertEqual(reality, my_expectation)
48
49
50# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: (1, 2, 3, 'n')"
             != 'I got: "(1, 2, 3, n)"'

GREEN: make it pass

I change the tuple_ in my_expectation to match reality

44    def test_passing_a_tuple(self):
45        reality = src.telephone.text((1, 2, 3, 'n'))
46        # my_expectation = 'I got: (1, 2, 3, n)'
47        my_expectation = "I got: (1, 2, 3, 'n')"
48        self.assertEqual(reality, my_expectation)
49
50
51# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add a variable to use to remove repetition of the tuple_

    44    def test_passing_a_tuple(self):
45        a_tuple = (1, 2, 3, 'n')
46        reality = src.telephone.text((1, 2, 3, 'n'))
47        # my_expectation = 'I got: (1, 2, 3, n)'
48        my_expectation = "I got: (1, 2, 3, 'n')"
49        self.assertEqual(reality, my_expectation)
50
51
52# Exceptions seen

  • I use the variable with string interpolation to remove repetition of the tuple_

    44    def test_passing_a_tuple(self):
45        a_tuple = (1, 2, 3, 'n')
46        # reality = src.telephone.text((1, 2, 3, 'n'))
47        reality = src.telephone.text(a_tuple)
48        # my_expectation = 'I got: (1, 2, 3, n)'
49        # my_expectation = "I got: (1, 2, 3, 'n')"
50        my_expectation = f"I got: {a_tuple}"
51        self.assertEqual(reality, my_expectation)
52
53
54# Exceptions seen

    the test is still green.

  • I remove the comments

    44    def test_passing_a_tuple(self):
45        a_tuple = (1, 2, 3, 'n')
46        reality = src.telephone.text(a_tuple)
47        my_expectation = f"I got: {a_tuple}"
48        self.assertEqual(reality, my_expectation)
49
50
51# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit --all --message 'add test_passing_a_tuple'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass a tuple from a test to a function.

test_passing_a_list

I can pass a list (anything in square brackets [ ]) from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for a list

    44    def test_passing_a_tuple(self):
45        a_tuple = (1, 2, 3, 'n')
46        reality = src.telephone.text(a_tuple)
47        my_expectation = f"I got: {a_tuple}"
48        self.assertEqual(reality, my_expectation)
49
50    def test_passing_a_list(self):
51        reality = src.telephone.text([1, 2, 3, 'n'])
52        my_expectation = 'I got: [1, 2, 3, "n"]'
53        self.assertEqual(reality, my_expectation)
54
55
56# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: [1, 2, 3, 'n']"
             != "I got: '[1, 2, 3, n]'"

GREEN: make it pass

I change the list in my_expectation to match reality

50    def test_passing_a_list(self):
51        reality = src.telephone.text([1, 2, 3, 'n'])
52        # my_expectation = 'I got: [1, 2, 3, "n"]'
53        my_expectation = "I got: [1, 2, 3, 'n']"
54        self.assertEqual(reality, my_expectation)
55
56
57# Exceptions seen

the test passes. Python_ changed the double quotes (") in the list to a single quote (').

REFACTOR: make it better

  • I add a variable to use to remove repetition of the list

    50    def test_passing_a_list(self):
51        a_list = [1, 2, 3, 'n']
52        reality = src.telephone.text([1, 2, 3, 'n'])
53        # my_expectation = 'I got: [1, 2, 3, "n"]'
54        my_expectation = "I got: [1, 2, 3, 'n']"
55        self.assertEqual(reality, my_expectation)
56
57
58# Exceptions seen

  • I use the variable with an f-string to remove repetition of the list

    50    def test_passing_a_list(self):
51        a_list = [1, 2, 3, 'n']
52        # reality = src.telephone.text([1, 2, 3, 'n'])
53        reality = src.telephone.text(a_list)
54        # my_expectation = 'I got: [1, 2, 3, "n"]'
55        # my_expectation = "I got: [1, 2, 3, 'n']"
56        my_expectation = f"I got: {a_list}"
57        self.assertEqual(reality, my_expectation)
58
59
60# Exceptions seen

    the test is still green.

  • I remove the comments

    50    def test_passing_a_list(self):
51        a_list = [1, 2, 3, 'n']
52        reality = src.telephone.text(a_list)
53        my_expectation = f"I got: {a_list}"
54        self.assertEqual(reality, my_expectation)
55
56
57# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit -am 'add test_passing_a_list'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass a list from a test to a function.

test_passing_a_dictionary

I can pass a dictionary (anything in curly braces { } separated by a comma) from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a test for a dictionary

    50    def test_passing_a_list(self):
51        a_list = [1, 2, 3, 'n']
52        reality = src.telephone.text(a_list)
53        my_expectation = f"I got: {a_list}"
54        self.assertEqual(reality, my_expectation)
55
56    def test_passing_a_dictionary(self):
57        reality = src.telephone.text(
58            {
59                'key1': 'value1',
60                'keyN': [0, 1, 2, 'n'],
61            }
62        )
63        my_expectation = (
64            "I got: "
65            "{key1: value1, keyN: [0, 1, 2, n]}"
66        )
67        self.assertEqual(reality, my_expectation)
68
69
70# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError:
    "I got: {'key1': 'value1', 'keyN': [0, 1, 2, 'n']}"
 != 'I got: { key1:   value1 ,  keyN : [0, 1, 2,  n ]}'

GREEN: make it pass

I change my_expectation to match reality

56    def test_passing_a_dictionary(self):
57        reality = src.telephone.text(
58            {
59                'key1': 'value1',
60                'keyN': [0, 1, 2, 'n'],
61            }
62        )
63        my_expectation = (
64            "I got: "
65            # "{key1: value1, keyN: [0, 1, 2, n]}"
66            "{'key1': 'value1', 'keyN': [0, 1, 2, 'n']}"
67        )
68        self.assertEqual(reality, my_expectation)
69
70
71# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add a variable to use to remove repetition of the dictionary

    56    def test_passing_a_dictionary(self):
57        a_dictionary = {
58            'key1': 'value1',
59            'keyN': [0, 1, 2, 'n'],
60        }
61        reality = src.telephone.text(
62            {
63                'key1': 'value1',
64                'keyN': [0, 1, 2, 'n'],
65            }
66        )
67        my_expectation = (
68            "I got: "
69            # "{key1: value1, keyN: [0, 1, 2, n]}"
70            "{'key1': 'value1', 'keyN': [0, 1, 2, 'n']}"
71        )
72        self.assertEqual(reality, my_expectation)
73
74
75# Exceptions seen

  • I use the variable with string interpolation to remove repetition of the dictionary

    56    def test_passing_a_dictionary(self):
57        a_dictionary = {
58            'key1': 'value1',
59            'keyN': [0, 1, 2, 'n'],
60        }
61        # reality = src.telephone.text(
62        #     {
63        #         'key1': 'value1',
64        #         'keyN': [0, 1, 2, 'n'],
65        #     }
66        # )
67        reality = src.telephone.text(a_dictionary)
68        # my_expectation = (
69        #     "I got: "
70        #     # "{key1: value1, keyN: [0, 1, 2, n]}"
71        #     "{'key1': 'value1', 'keyN': [0, 1, 2, 'n']}"
72        # )
73        my_expectation = f'I got: {a_dictionary}'
74        self.assertEqual(reality, my_expectation)
75
76
77# Exceptions seen

    the test is still green.

  • I remove the comments

    56    def test_passing_a_dictionary(self):
57        a_dictionary = {
58            'key1': 'value1',
59            'keyN': [0, 1, 2, 'n'],
60        }
61        reality = src.telephone.text(a_dictionary)
62        my_expectation = f'I got: {a_dictionary}'
63        self.assertEqual(reality, my_expectation)
64
65
66# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit --all --message 'add test_passing_a_dictionary'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass a dictionary from a test to a function.

test_passing_a_class

I can pass an object from a test to a function

RED: make it fail

  • I go back to the terminal_ that is running the tests

  • I add a failing test to see what happens when I pass a class from a test to the text function, in test_telephone.py

    56    def test_passing_a_dictionary(self):
57        a_dictionary = {
58            'key1': 'value1',
59            'keyN': [0, 1, 2, 'n'],
60        }
61        reality = src.telephone.text(a_dictionary)
62        my_expectation = f'I got: {a_dictionary}'
63        self.assertEqual(reality, my_expectation)
64
65    def test_passing_a_class(self):
66        reality = src.telephone.text(object)
67        my_expectation = 'I got: object'
68        self.assertEqual(reality, my_expectation)
69
70
71# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'object'>"
             != 'I got:         object'

    object is the mother class that all Python classes come from, and everything in Python_ is an object

GREEN: make it pass

I change my_expectation to match reality

65    def test_passing_a_class(self):
66        reality = src.telephone.text(object)
67        # my_expectation = 'I got: object'
68        my_expectation = "I got: <class 'object'>"
69        self.assertEqual(reality, my_expectation)
70
71
72# Exceptions seen

the test passes.

REFACTOR: make it better

  • I add another assertion with the TestTelephone class to test_passing_a_class in test_telephone.py

    65    def test_passing_a_class(self):
66        reality = src.telephone.text(object)
67        # my_expectation = 'I got: object'
68        my_expectation = "I got: <class 'object'>"
69        self.assertEqual(reality, my_expectation)
70
71        reality = src.telephone.text(TestTelephone)
72        my_expectation = "I got: <class 'object'>"
73        self.assertEqual(reality, my_expectation)
74
75
76# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError:
    "I got: <class 'tests.test_telephone.TestTelephone'>"
 != "I got: <class 'object'>"

  • I change my_expectation to match reality

    71        reality = src.telephone.text(TestTelephone)
72        # my_expectation = "I got: <class 'object'>"
73        my_expectation = (
74            "I got: <class"
75            f" 'tests.test_telephone.TestTelephone'>"
76        )
77        self.assertEqual(reality, my_expectation)
78
79
80# Exceptions seen

    the test passes. What does tests.test_telephone.TestTelephone point to?

    • tests is the folder_

    • test_telephone is test_telephone.py in the tests folder_

    • TestTelephone is the class (object) that is defined on line 5 of test_telephone.py in the tests folder_

  • I add another assertion

    71        reality = src.telephone.text(TestTelephone)
72        # my_expectation = "I got: <class 'object'>"
73        my_expectation = (
74            "I got: <class"
75            f" 'tests.test_telephone.TestTelephone'>"
76        )
77        self.assertEqual(reality, my_expectation)
78
79        reality = src.telephone.text(self)
80        my_expectation = "I got: self"
81        self.assertEqual(reality, my_expectation)
82
83
84# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError:
    'I got: test_passing_a_class (
        tests.test_telephone
             .TestTelephone.test_passing_a_class
    )'
    != 'I got: self'

  • I change my_expectation to match reality

    79        reality = src.telephone.text(self)
80        # my_expectation = "I got: self"
81        my_expectation = (
82            "I got: test_passing_a_class"
83            " (tests.test_telephone.TestTelephone"
84            ".test_passing_a_class)"
85        )
86        self.assertEqual(reality, my_expectation)
87
88
89# Exceptions seen

  • I add an assertion for bool (the class for booleans)

    79        reality = src.telephone.text(self)
80        # my_expectation = "I got: self"
81        my_expectation = (
82            "I got: test_passing_a_class"
83            " (tests.test_telephone.TestTelephone"
84            ".test_passing_a_class)"
85        )
86        self.assertEqual(reality, my_expectation)
87
88        reality = src.telephone.text(bool)
89        my_expectation = 'I got: bool'
90        self.assertEqual(reality, my_expectation)
91
92
93# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'bool'>" != 'I got: bool'

  • I change my_expectation to match reality

    88        reality = src.telephone.text(bool)
89        # my_expectation = 'I got: bool'
90        my_expectation = "I got: <class 'bool'>"
91        self.assertEqual(reality, my_expectation)
92
93
94# Exceptions seen

    the test passes.

  • I add an assertion for int_ (the class for whole numbers without decimals)

    88        reality = src.telephone.text(bool)
89        # my_expectation = 'I got: bool'
90        my_expectation = "I got: <class 'bool'>"
91        self.assertEqual(reality, my_expectation)
92
93        reality = src.telephone.text(int)
94        my_expectation = "I got: int"
95        self.assertEqual(reality, my_expectation)
96
97
98# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'int'>" != 'I got: int'

  • I change my_expectation to match reality

    93        reality = src.telephone.text(int)
94        # my_expectation = "I got: int"
95        my_expectation = "I got: <class 'int'>"
96        self.assertEqual(reality, my_expectation)
97
98
99# Exceptions seen

    the test passes

  • I add an assertion for float_ (the class for binary floating point decimal numbers)

     93        reality = src.telephone.text(int)
 94        # my_expectation = 'I got: int'
 95        my_expectation = "I got: <class 'int'>"
 96        self.assertEqual(reality, my_expectation)
 97
 98        reality = src.telephone.text(float)
 99        my_expectation = "I got: float"
100        self.assertEqual(reality, my_expectation)
101
102
103# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'float'>" != 'I got: float'

  • I change my_expectation to match reality

     98        reality = src.telephone.text(float)
 99        # my_expectation = "I got: float"
100        my_expectation = "I got: <class 'float'>"
101        self.assertEqual(reality, my_expectation)
102
103
104# Exceptions seen

    the test passes

  • I add an assertion for str_ (the class for anything in quotes)

     98        reality = src.telephone.text(float)
 99        # my_expectation = "I got: float"
100        my_expectation = "I got: <class 'float'>"
101        self.assertEqual(reality, my_expectation)
102
103        reality = src.telephone.text(str)
104        my_expectation = "I got: str"
105        self.assertEqual(reality, my_expectation)
106
107
108# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'str'>" != 'I got: str'

  • I change my_expectation to match reality

    103        reality = src.telephone.text(str)
104        # my_expectation = "I got: str"
105        my_expectation = "I got: <class 'str'>"
106        self.assertEqual(reality, my_expectation)
107
108
109# Exceptions seen

    the test passes

  • I add an assertion for tuple_ (the class for anything in parentheses ( ) separated by a comma)

    103        reality = src.telephone.text(str)
104        # my_expectation = "I got: str"
105        my_expectation = "I got: <class 'str'>"
106        self.assertEqual(reality, my_expectation)
107
108        reality = src.telephone.text(tuple)
109        my_expectation = "I got: tuple"
110        self.assertEqual(reality, my_expectation)
111
112
113# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'tuple'>" != 'I got: tuple'

  • I change my_expectation to match reality

    108        reality = src.telephone.text(tuple)
109        # my_expectation = "I got: tuple"
110        my_expectation = "I got: <class 'tuple'>"
111        self.assertEqual(reality, my_expectation)
112
113
114# Exceptions seen

  • I add an assertion for list (the class for anything in square brackets ‘[ ]’)

    108        reality = src.telephone.text(tuple)
109        # my_expectation = "I got: tuple"
110        my_expectation = "I got: <class 'tuple'>"
111        self.assertEqual(reality, my_expectation)
112
113        reality = src.telephone.text(list)
114        my_expectation = "I got: list"
115        self.assertEqual(reality, my_expectation)
116
117
118# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'list'>" != 'I got: list'

  • I change my_expectation to match reality

    113        reality = src.telephone.text(list)
114        # my_expectation = "I got: list"
115        my_expectation = "I got: <class 'list'>"
116        self.assertEqual(reality, my_expectation)
117
118
119# Exceptions seen

    the test passes

  • I add an assertion for set_ (the class anything in curly braces { } separated by a comma)

    113        reality = src.telephone.text(list)
114        # my_expectation = "I got: list"
115        my_expectation = "I got: <class 'list'>"
116        self.assertEqual(reality, my_expectation)
117
118        reality = src.telephone.text(set)
119        my_expectation = "I got: set"
120        self.assertEqual(reality, my_expectation)
121
122
123# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'set'>" != 'I got: set'

  • I change my_expectation to match reality

    118        reality = src.telephone.text(set)
119        # my_expectation = "I got: set"
120        my_expectation = "I got: <class 'set'>"
121        self.assertEqual(reality, my_expectation)
122
123
124# Exceptions seen

    the test passes

  • I add an assertion for dict (the class for any key-value pairs in curly braces ‘{ }’ separated by a comma)

    118        reality = src.telephone.text(set)
119        # my_expectation = "I got: set"
120        my_expectation = "I got: <class 'set'>"
121        self.assertEqual(reality, my_expectation)
122
123        reality = src.telephone.text(dict)
124        my_expectation = "I got: dict"
125        self.assertEqual(reality, my_expectation)
126
127
128# Exceptions seen

    the terminal_ is my friend, and shows AssertionError

    AssertionError: "I got: <class 'dict'>" != 'I got: dict'

  • I change my_expectation to match reality

    123        reality = src.telephone.text(dict)
124        # my_expectation = "I got: dict"
125        my_expectation = "I got: <class 'dict'>"
126        self.assertEqual(reality, my_expectation)
127
128
129# Exceptions seen

    the test passes

  • I remove the commented lines

     65    def test_passing_a_class(self):
 66        reality = src.telephone.text(object)
 67        my_expectation = "I got: <class 'object'>"
 68        self.assertEqual(reality, my_expectation)
 69
 70        reality = src.telephone.text(TestTelephone)
 71        my_expectation = (
 72            "I got: <class"
 73            f" 'tests.test_telephone.TestTelephone'>"
 74        )
 75        self.assertEqual(reality, my_expectation)
 76
 77        reality = src.telephone.text(self)
 78        my_expectation = (
 79            "I got: test_passing_a_class"
 80            " (tests.test_telephone.TestTelephone"
 81            ".test_passing_a_class)"
 82        )
 83        self.assertEqual(reality, my_expectation)
 84
 85        reality = src.telephone.text(bool)
 86        my_expectation = "I got: <class 'bool'>"
 87        self.assertEqual(reality, my_expectation)
 88
 89        reality = src.telephone.text(int)
 90        my_expectation = "I got: <class 'int'>"
 91        self.assertEqual(reality, my_expectation)
 92
 93        reality = src.telephone.text(float)
 94        my_expectation = "I got: <class 'float'>"
 95        self.assertEqual(reality, my_expectation)
 96
 97        reality = src.telephone.text(str)
 98        my_expectation = "I got: <class 'str'>"
 99        self.assertEqual(reality, my_expectation)
100
101        reality = src.telephone.text(tuple)
102        my_expectation = "I got: <class 'tuple'>"
103        self.assertEqual(reality, my_expectation)
104
105        reality = src.telephone.text(list)
106        my_expectation = "I got: <class 'list'>"
107        self.assertEqual(reality, my_expectation)
108
109        reality = src.telephone.text(set)
110        my_expectation = "I got: <class 'set'>"
111        self.assertEqual(reality, my_expectation)
112
113        reality = src.telephone.text(dict)
114        my_expectation = "I got: <class 'dict'>"
115        self.assertEqual(reality, my_expectation)
116
117
118# Exceptions seen

  • I add a git_ commit message in the other terminal_

    git commit -am 'add test_passing_a_class'

    the terminal_ shows a summary of the changes then goes back to the command line.

I can pass an object from a test to a function.

test_telephone

Time to write the program_ that makes the tests pass without looking at test_telephone.py

RED: make it fail

  • I close test_telephone.py in the editor

  • I delete the text in telephone.py and the terminal_ shows 9 failures. I start with the last AttributeError

    FAILED ...test_passing_a_class - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_a_dictionary - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_a_float - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_a_list - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_a_string - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_a_tuple - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_an_integer - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_booleans - AttributeError:
        module 'src.telephone' has no attribute 'text'
FAILED ...test_passing_none - AttributeError:
        module 'src.telephone' has no attribute 'text'

GREEN: make it pass

  • I add the name to telephone.py

    1text

    the terminal_ is my friend, and shows NameError

    NameError: name 'text' is not defined

  • I point it to None to define it

    1# text
2text = None

    the terminal_ is my friend, and shows TypeError

    TypeError: 'NoneType' object is not callable

  • I make text a function to make it callable_

    1# text
2# text = None
3def text():
4    return None

    the terminal_ is my friend, and shows TypeError

    TypeError: text() takes 0 positional arguments
           but 1 was given

  • I make the function take input

    1# text
2# text = None
3# def text():
4def text(value):
5    return None

    the terminal_ is my friend, and shows AssertionError

    AssertionError: None != 'I got: None'

  • I copy the string_ from the terminal_ and paste it in the `return statement`_ to match the expectation of the test

    1# text
2# text = None
3# def text():
4def text(value):
5    # return None
6    return 'I got: None'

    the terminal_ is my friend, and shows AssertionError

    AssertionError: 'I got: None' != 'I got: False'

  • I add a `return statement`_ to see the difference between the input and the expected output (remember the identity function?)

    1# text
2# text = None
3# def text():
4def text(value):
5    # return None
6    # return 'I got: None'
7    return value

    the test summary info shows that every test has AssertionError

    AssertionError:
    <class 'object'> != "I got: <class 'object'>"
AssertionError:
             {'key1': 'value1', 'keyN': [0, 1, 2, 'n']}
  != "I got: {'key1': 'value1', 'keyN': [0, 1, 2, 'n']}"
AssertionError:
    1.234 != 'I got: 1.234'
AssertionError:
    [1, 2, 3, 'n'] != "I got: [1, 2, 3, 'n']"
AssertionError:
    'hello' != 'I got: hello'
AssertionError:
    (1, 2, 3, 'n') != "I got: (1, 2, 3, 'n')"
AssertionError:
    1234 != 'I got: 1234'
AssertionError:
    False != 'I got: False'
AssertionError:
    None != 'I got: None'

    they all expect the input (value) as part of the message

  • I add a `return statement`_ with an f-string

    1# text
2# text = None
3# def text():
4def text(value):
5    # return None
6    # return 'I got: None'
7    # return value
8    return f'I got: {value}'

    and all the tests are passing! I am a programmer!!

  • I remove the commented lines

    1def text(value):
2    return f'I got: {value}'

close the project

  • I close telephone.py in the editor

  • I click in the terminal_ where the tests are running, then use q on the keyboard to leave the tests. The terminal_ goes back to the command line.

  • I `change directory`_ to the parent of telephone

    cd ..

    the terminal_ shows

    .../pumping_python

    I am back in the pumping_python directory_

review

Here are the tests I ran to see what happens when I pass Python basic data structures from a test to a program_ and place them in an f-string which is one way to do string interpolation

I also saw these Exceptions

code from the chapter

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

what is next?

You now know:

would you like to test using dictionaries and functions to make a person?

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