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Build and test a command and return its output

Constraint

Base time: 2 workday (Max: 4)

Hill chart

  .
 . .
.   +
0-1-2

Place, Affordance, Connection

  • Affordance users can act

    • List sections python coda.py list-sections

  • Connection users are taken to

    • python coda.py list-sections --> list_sections() --> Coda() --> objCoda.list_sections() --> pycoda.list_sections() --> codaio.list_sections() --> Dict --> Json --> Stdout

Test driven development of a command

When you approach coding using a test driven development ["TDD"], you start with a test case and then build your code around the test case. You can have have one or more test cases for each feature.

In our example, we a command that allows users to list sections in a document. There are two cases that we test for:

  • Exit code is 0
  • Json output contains a string Section.

In our first test case, with reference to our connection where users are taken to, this fails if the environment variable CODA_API_KEY is not configured, or if the docID is invalid.

The second test case, with reference to our places where users can navigate, this fails if the docID is invalid.

Create test case

  1. Edit the tests/test_coda.py file and append the following lines of code:
strDoc='QlIwnjdg3j'

def test_list_sections():
  runner = CliRunner()
  result = runner.invoke(clickMain, ['list-sections', '--doc', strDoc])
  assert result.exit_code == 0
  assert "page" in result.output 

def main():
  ...
  test_list_sections()

Configure build

  1. Install Python packages

Before we can run our app, we need to activate virtual environment and install any dependencies. We use the flag --dev to specify that these packages are for development only.

cd app
pipenv shell
pipenv install --dev pytest=6.2.4

Build the command

With reference to our connection where users are taken to:

  • python coda.py list-sections --> list_sections() --> Coda() --> objCoda.list_sections() --> pycoda.list_sections() --> codaio.list_sections() --> Dict --> Json --> Stdout

When a user makes a list-sections command, the coda.py calls the global function list_sections(), that in turn calls the method list_sections() of instance ctx.obj, which is an object of the Coda class.

This method of instance ctx.obj calls your custom wrapper function list_sections() of instance objCoda, which is an object of the Pycoda class. Your custom library calls the function list_sections from the package codaio, which returns a dictionary. This is parsed by your function and translated to a Json return value.

  1. Edit the coda.py file in the path app/. Modify the following lines of code:
class Coda(object):
  ...
  def list_sections(self, strDocId):
    result = self.objCoda.list_sections(strDocId)
    print ( result )

"""--------+---------+---------+---------+---------+---------+---------+---------+---------|
|                         L I S T _ S E C T I O N S   C O M M A N D                        |
|----------+---------+---------+---------+---------+---------+---------+---------+-------"""
@clickMain.command()
@click.option('--doc', required=True)
@click.pass_obj
#---------
# Function 
def list_sections(objCoda, doc):
  """ Returns the list of sections in a doc """
  objCoda.list_sections(doc)
  1. Edit the pycoda.py file in the path app/. Add the following lines of code:
class Pycoda():
  ...
  def list_sections(self, strDocId):
    """ Returns a list of sections in DocId """
    assert(strDocId)
    list = self.coda.list_sections(strDocId)
    strRet=""
    for doc in list:
      if doc == "items":
        for obj in list[doc]:
          strRet=strRet+json.dumps(obj)
    return strRet