1 - Setting and getting code coverage
Switch to a new branch
Pull the latest frommain andcreate a new branchstep1
git checkout maingit pullgit checkout -b 'step1'Add a calculator backend
Let's continue by adding in our calculator logic. Create the fileapi/calculator.py with the following contents:
class Calculator: def add(x, y): return x + y def subtract(x, y): return x - y def multiply(x, y): return x * y def divide(x, y): if y == 0: return 'Cannot divide by 0' return x * 1.0 / yWe are defining aCalculator class that canadd,subtract,multiply, anddivide. Next, we are going to create a simple Flask server to run our calculator app. Create a fileapi/app.py
from flask import ( Flask, request,)from api.calculator import Calculatorapp = Flask(__name__)@app.route('/api/add', methods=['POST'])def add(): return operation('add', 2)@app.route('/api/subtract', methods=['POST'])def subtract(): return operation('subtract', 2)@app.route('/api/multiply', methods=['POST'])def multiply(): return operation('multiply', 2)@app.route('/api/divide', methods=['POST'])def divide(): return operation('divide', 2)def operation(method, num_factors): factors = [] if num_factors == 2: factors.append(float(request.json.get('x'))) factors.append(float(request.json.get('y'))) return str(getattr(Calculator, method)(*factors))The server acceptsPOST requests to the/api/add,/api/subtract,/api/multiply, and/api/divide endpoints. It expects to receiveJSON valuesx andy as data.
Run the server
You can start the server by running
flask --app api/app runYou can test if the server is running by hitting one of the above endpoints. Try it by running the command below from a new terminal.
curl -d '{"x": 1, "y": 2}' -H 'Content-Type: application/json' http://127.0.0.1:5000/api/addYou can see that the server is adding1 and2 together and returning3.0
Add backend tests
Let's add some tests for our calculator. Create a new directorytests inapi and add a blank__init__.py file and atest_calculator.py file.
mkdir api/teststouch api/tests/__init__.pytouch api/tests/test_calculator.pyAdd this totest_calculator.py.
from ..calculator import Calculatordef test_add(): assert Calculator.add(1, 2) == 3.0 assert Calculator.add(1.0, 2.0) == 3.0 assert Calculator.add(0, 2.0) == 2.0 assert Calculator.add(2.0, 0) == 2.0 assert Calculator.add(-4, 2.0) == -2.0def test_subtract(): assert Calculator.subtract(1, 2) == -1.0 assert Calculator.subtract(2, 1) == 1.0 assert Calculator.subtract(1.0, 2.0) == -1.0 assert Calculator.subtract(0, 2.0) == -2.0 assert Calculator.subtract(2.0, 0.0) == 2.0 assert Calculator.subtract(-4, 2.0) == -6.0def test_multiply(): assert Calculator.multiply(1, 2) == 2.0 assert Calculator.multiply(1.0, 2.0) == 2.0 assert Calculator.multiply(0, 2.0) == 0.0 assert Calculator.multiply(2.0, 0.0) == 0.0 assert Calculator.multiply(-4, 2.0) == -8.0def test_divide(): assert Calculator.divide(1, 2) == 0.5 assert Calculator.divide(1.0, 2.0) == 0.5 assert Calculator.divide(0, 2.0) == 0 assert Calculator.divide(-4, 2.0) == -2.0Run the tests and collect code coverage
To run tests in a terminal:
pytestHowever, we are more curious about the code coverage of ourcalculator class. We can use the command
pytest --cov api/to show us coverage results. Doing this should give you a report that looks like
Name Stmts Miss Cover--------------------------------------------------api/__init__.py 0 0 100%api/app.py 22 22 0%api/calculator.py 11 1 91%api/tests/__init__.py 0 0 100%api/tests/test_calculator.py 25 0 100%--------------------------------------------------TOTAL 58 23 61%Notice thatapi/app.py isn’t covered, as we haven’t tested the Flask application, but ourapi/calculator.py file is missing tests on one line of code.
Commit and merge your changes
You can commit this code by running
git add .git commit -m 'step1: add calculator backend and tests'git push origin step1Create a merge request on GitLab and merge the changes.
When opening merge requests, be sure to select your own repository as the target branch, orset your project's default target branch
Updated 19 days ago