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preggy is an assertion library for Python.** What were you `expect`ing?

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preggy

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preggy is an assertion library for Python. What were you expecting?

Extracted from the PyVows project.

Installing

We recommend using pip:

pip install preggy

Usage

Simply tell your test what to expect():

from preggy import expect

def test_roses_are_red():
    rose = Rose()
    expect(rose.color).to_equal('red')

def test_violets_are_not_red():
    violet = Violet()
    expect(violet.color).not_to_equal('red')

Built-in Expectations

Equality

expect(4).to_equal(4)
expect(5).Not.to_equal(4)
expect(5).not_to_equal(4)  # same as previous

Comparison

expect(4).to_be_lesser_than(5)
expect(5).to_be_greater_than(4)
expect(5).Not.to_be_lesser_than(4)
expect(4).not_to_be_greater(5)  # same as previous

expect(4).to_be_lesser_or_equal_to(5)
expect(4).to_be_lesser_or_equal_to(4)
expect(5).not_to_be_lesser_or_equal_to(4)

expect(5).to_be_greater_or_equal_to(4)
expect(5).to_be_greater_or_equal_to(5)
expect(4).not_to_be_greater_or_equal_to(5)

expect("b").to_be_greater_than("a")
expect("a").to_be_lesser_than("b")

expect([1, 2, 3]).to_be_greater_than([1, 2])  # comparing using length
expect((1, 2, 3)).to_be_greater_than((1, 2))  # comparing using length
expect({ "a": "b", "c": "d" }).to_be_greater_than({ "a": "b" })  # comparing using length of keys

Similarity

expect('sOmE RandOm     CAse StRiNG').to_be_like('some random case string')

expect(1).to_be_like(1)
expect(1).to_be_like(1.0)
expect(1).to_be_like(long(1))

expect([1, 2, 3]).to_be_like([3, 2, 1])
expect([1, 2, 3]).to_be_like((3, 2, 1))
expect([[1, 2], [3,4]]).to_be_like([4, 3], [2, 1]])

expect({ 'some': 1, 'key': 2 }).to_be_like({ 'key': 2, 'some': 1 })

expect('sOmE RandOm     CAse StRiNG').Not.to_be_like('other string')
expect('sOmE RandOm     CAse StRiNG').not_to_be_like('other string')  # same as previous

expect(1).not_to_be_like(2)
expect([[1, 2], [3,4]]).not_to_be_like([4, 4], [2, 1]])
expect({ 'some': 1, 'key': 2 }).not_to_be_like({ 'key': 3, 'some': 4 })

Type

expect(os.path).to_be_a_function()
expect(1).to_be_numeric()
expect({ 'some': 1, 'key': 2 }).to_be_instance_of(dict)
expect(open(__file__)).to_be_a_file()

expect('some').Not.to_be_a_function()
expect('some').Not.to_be_numeric()
expect('some').Not.to_be_instance_of(dict)
expect('some').Not.to_be_a_file()

True / False

expect(True).to_be_true()
expect('some').to_be_true()
expect([1, 2, 3]).to_be_true()
expect({ 'a': 'b' }).to_be_true()
expect(1).to_be_true()

expect(False).to_be_false()  # not_to_be_true() would work, too. but, it's so...eww
expect(None).to_be_false()
expect('').to_be_false()
expect(0).to_be_false()
expect([]).to_be_false()
expect({}).to_be_false()

None

expect(None).to_be_null()
expect('some').Not.to_be_null()
expect('some').not_to_be_null()  # same as previous

Inclusion

expect([1, 2, 3]).to_include(2)
expect((1, 2, 3)).to_include(2)
expect('123').to_include('2')
expect({ 'a': 1, 'b': 2, 'c': 3}).to_include('b')

expect([1, 3]).Not.to_include(2)  # or, exclusion...

Regular Expressions

expect('some').to_match(r'^[a-z]+')
expect('Some').Not.to_match(r'^[a-z]+')

Length

expect([1, 2, 3]).to_length(3)
expect((1, 2, 3)).to_length(3)
expect('abc').to_length(3)
expect({ 'a': 1, 'b': 2, 'c': 3}).to_length(3)
expect(lifo_queue).to_length(2)
expect(queue).to_length(3)

expect([1]).Not.to_length(3)
expect([1]).not_to_length(3)  # same as previous

Emptiness

expect([]).to_be_empty()
expect(tuple()).to_be_empty()
expect({}).to_be_empty()
expect('').to_be_empty()

expect([1]).not_to_be_empty()
expect((1,2)).not_to_be_empty()
expect({'a': 1}).not_to_be_empty()
expect('roses are red').not_to_be_empty()

Exceptions

expect(RuntimeError()).to_be_an_error() 
expect(RuntimeError()).to_be_an_error_like(RuntimeError)
expect(ValueError('error')).to_have_an_error_message_of('error')

expect("I'm not an error").Not.to_be_an_error()
expect(ValueError()).Not.to_be_an_error_like(RuntimeError)
expect(ValueError('some')).Not.to_have_an_error_message_of('error')

# when expecting a method to error
err = expect.error_to_happen(RuntimeError)  # attribute to a variable so you can use the exception later

with err:
    raise RuntimeError("something is wrong")

expect(err).to_have_an_error_message_of('something is wrong')

# or the shorter version
with expect.error_to_happen(RuntimeError, message="something is wrong"):
    raise RuntimeError("something is wrong")

# or if you don't care about the message:
with expect.error_to_happen(RuntimeError):
    raise RuntimeError("something is wrong")

# or if you need to make sure error does not happen
with expect.error_not_to_happen(RuntimeError, message="something is wrong"):
    raise RuntimeError("something is wrong")  # Fails with AssertionError

# or if you don't care about the message, only that the error does not happen:
with expect.error_not_to_happen(RuntimeError):
    raise RuntimeError("something is wrong")  # Fails with AssertionError

Failure

expect.not_to_be_here()  # raises AssertionError

# raises AssertionError with error message
expect.not_to_be_here("some error message")

Chained Assertions

# assertions may be chained, for brevity:
expect(6).not_to_be_null().to_equal(6)

# a more *sensible* example:
expect(foo).not_to_be_null().to_equal(expected.get('foo'))

Contributing

See CONTRIBUTING.

License

The MIT License (MIT)

Copyright (c) 2013 Bernardo Heynemann heynemann@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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