truth table: Nullary and Unary Operations

requirements

how to make a python test driven development environment with truth_table as the name of the project

Nullary Operations

There are 2 Nullary operations, they do not take input and always return the same value, they are singleton functions

test_logical_true

red: make it fail

I change the text in test_truth_table.py

import unittest
import src.truth_table


class TestNullaryOperations(unittest.TestCase):

    def test_logical_true(self):
        self.assertTrue(src.truth_table.logical_true())

and the terminal shows AttributeError

AttributeError: module 'src.truth_table' has no attribute 'logical_true'

green: make it pass

I add it to the list of Exceptions encountered

# Exceptions Encountered
# AssertionError
# AttributeError

then I add a function to truth_table.py

def logical_true():
    return None

the terminal shows AssertionError

AssertionError: None is not true

I change False to True in the return statement

def logical_true():
    return True

and the test passes

test_logical_false

red: make it fail

I add another test

def test_logical_true(self):
    self.assertTrue(src.truth_table.logical_true())

def test_logical_false(self):
    self.assertFalse(src.truth_table.logical_false())

the terminal shows AttributeError

AttributeError: module 'src.truth_table' has no attribute 'logical_false'. Did you mean: 'logical_true'?

green: make it pass

  • I add a function definition to truth_table.py

    def logical_true():
    return True


def logical_false():
    return True

    and the terminal shows AssertionError

    AssertionError: True is not false

  • When I change True to False in the return statement

    def logical_false():
    return False

    the test passes

Unary Operations

There are 2 unary operations, they each take one input

test_logical_identity

red: make it fail

I add a new TestCase and a test to test_truth_table.py

class TestNullaryOperations(unittest.TestCase):
    ...


class TestUnaryOperations(unittest.TestCase):

    def test_logical_identity(self):
        self.assertTrue(src.truth_table.logical_identity(True))

the terminal shows AttributeError

AttributeError: module 'src.truth_table' has no attribute 'logical_identity'

green: make it pass

  • I add the function

    def logical_false():
    return False


def logical_identity():
    return False

    the terminal shows TypeError

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

    I add the error to the list of Exceptions encountered

    # Exceptions Encountered
# AssertionError
# AttributeError
# TypeError

    then I add a parameter

    def logical_identity(argument):
    return False

    and the terminal shows AssertionError

    AssertionError: False is not true

    I change the return statement

    def logical_identity(argument):
    return True

    and the test passes

refactor: make it better

I add another line to the test

def test_logical_identity(self):
    self.assertTrue(src.truth_table.logical_identity(True))
    self.assertFalse(src.truth_table.logical_identity(False))

the terminal shows AssertionError

AssertionError: True is not false

when I change the return statement

def logical_identity(argument):
    return False

the terminal shows AssertionError

AssertionError: False is not true

there is a failure for the line that passed before. The expectation of the test is that when True is given, the result is True and when False is given, the result is False. I make logical_identity return its input

def logical_identity(argument):
    return argument

and the terminal shows passing tests. logical_identity is a passthrough function, it returns its input as output.

test_logical_negation

red: make it fail

I add a new test

def test_logical_identity(self):
    self.assertTrue(src.truth_table.logical_identity(True))
    self.assertFalse(src.truth_table.logical_identity(False))

def test_logical_negation(self):
    self.assertFalse(src.truth_table.logical_negation(True))

the terminal shows AttributeError

AttributeError: module 'src.truth_table' has no attribute 'logical_negation'

green: make it pass

  • I add a definition for it

    def logical_identity(argument):
    return argument


def logical_negation(argument):
    return argument

    the terminal shows AssertionError

    AssertionError: True is not false

    when I make it return False

    def logical_negation(argument):
    return False

    the terminal shows passing tests

refactor: make it better

  • I add the next case

    def test_logical_negation(self):
    self.assertFalse(src.truth_table.logical_negation(True))
    self.assertTrue(src.truth_table.logical_negation(False))

    the terminal shows AssertionError

    AssertionError: False is not true

    I change the return statement

    def logical_negation(argument):
    return True

    and the terminal shows AssertionError

    AssertionError: True is not false

    it fails for the line that passed before. When I make the function return its input

    def logical_negation(argument):
    return argument

    the terminal shows AssertionError

    AssertionError: True is not false

    the expectation of the test is that when True is given, the result is False and when False is given, the result is True, I can make that happen with the not keyword

    def logical_negation(argument):
    return not argument

    and the terminal shows passing tests. logical_negation returns the opposite of its input

  • I change the name of the test

    def test_logical_negation_aka_not(self):
    self.assertFalse(src.truth_table.logical_negation(True))
    self.assertFalse(src.truth_table.logical_negation(False))

review

I ran tests for Nullary and Unary operations. Would you like to test binary operations?

truth table: tests and solutions