Add automated testing

[cclauss]

The goal of this change is to have Travis-CI automatically run flake8 tests on every pull request. This will help contributors know if their submissions are going to break the build. To turn on this free service, you would need to do steps 1 and 2 of https://docs.travis-ci.com/user/getting-started/

[polyzen]

Is Trusty needed for this? If not, I would omit the first two lines. sudo: false is the default, and Trusty will start to be the default next week, anyhow.

[polyzen]

You could also omit the patch versions.

[donnemartin]

Hi @cclauss @polyzen thanks for the PR and comments! I think I'm a little confused...with many of the code samples not being fully runnable (ie some are pseudocode or stubbed out), how does that affect the need and effectiveness of automated testing?

[cclauss]

People are going to assume that files with filenames that end in .py contain valid, executable Python code. Flakes8 verifies this. If the filename ends in .py then flake8 is going to scan the file looking for and flagging any text which is not valid Python code.

For your files to get a passing grade you have at least three options:

1. End the filenames of the files containing pseudocode with .txt, .md, etc. but not .py
2. Comment out the pseudocode with a leading #
3. Put the pseudocode inside triple quotes ''' ''' or """ """

[cclauss]

#98 demonstrates how we can modify the code to be lintable but still clearly indicate where the user needs to add code.

[cclauss]

This is what the output looks like before #98

• https://travis-ci.org/cclauss/itinerant-tester/jobs/272386243#L485

[cclauss]

I understand that we are treating these files largely as pseudocode but I still believe that this PR is required. It is a distraction for readers who know Python if the psudocode that they are reading contains syntax errors and variable names that do not match up.

[cclauss]

The output is looking better but we still have to correct one syntax error and 10 undefined names.

#149 Resolves the syntax error and 4 of the undefined names.

[cclauss]

#149 has been merged so the syntax error is resolved and we are down to seven undefined names.

• Add missing enum imports #157 (Enum) will close two of those undefined names
• Where is 'State' defined in social_graph_snippets.py? #148 (State) would close three more
• Adding missing self variable #158 (levels) would close one more
• Change variable seller to category in Mint solution #159 (category) would close the last undefined name

flake8 testing of https://github.com/donnemartin/system-design-primer on Python 3.6.3

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./solutions/object_oriented_design/online_chat/online_chat.py:98:21: F821 undefined name 'Enum'
class RequestStatus(Enum):
                    ^
./solutions/object_oriented_design/parking_lot/parking_lot.py:67:22: F821 undefined name 'levels'
        for level in levels:
                     ^
./solutions/system_design/mint/mint_mapreduce.py:36:28: F821 undefined name 'category'
            yield (period, category), amount
                           ^
./solutions/system_design/mint/mint_snippets.py:3:25: F821 undefined name 'Enum'
class DefaultCategories(Enum):
                        ^
./solutions/system_design/social_graph/social_graph_snippets.py:12:30: F821 undefined name 'State'
        source.visit_state = State.visited
                             ^
./solutions/system_design/social_graph/social_graph_snippets.py:19:49: F821 undefined name 'State'
                if adjacent_node.visit_state == State.unvisited:
                                                ^
./solutions/system_design/social_graph/social_graph_snippets.py:21:49: F821 undefined name 'State'
                    adjacent_node.visit_state = State.visited
                                                ^
7     F821 undefined name 'Enum'
7

[cclauss]

After more merges, we are down to just two items one item before these tests will pass.

• Change variable seller to category in Mint solution #159 (category) would close one undefined name
• Where is 'State' defined in social_graph_snippets.py? #148 (State) would close three more

flake8 testing of https://github.com/donnemartin/system-design-primer on Python 3.6.3

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./solutions/system_design/social_graph/social_graph_snippets.py:12:30: F821 undefined name 'State'
        source.visit_state = State.visited
                             ^
./solutions/system_design/social_graph/social_graph_snippets.py:19:49: F821 undefined name 'State'
                if adjacent_node.visit_state == State.unvisited:
                                                ^
./solutions/system_design/social_graph/social_graph_snippets.py:21:49: F821 undefined name 'State'
                    adjacent_node.visit_state = State.visited
                                                ^
3     F821 undefined name 'State'
3

[cclauss]

Given recent pull requests, these flake8 tests pass.

[cclauss]

@polyzen Can I please get your review on these proposed changes?

• https://github.com/donnemartin/system-design-primer/pull/93/files and click Review changes

[cclauss]

Bump on this one?