Coverage reporting in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start coverage measurement in a Flask app test.

Flask

import coverage
cov = coverage.[1]()
cov.start()

Drag options to blanks, or click blank then click option'

ACoverage

Bstart

Ccoverage

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'coverage' instead of 'Coverage'

Calling 'start' instead of creating the coverage object

The Coverage() class from the coverage module is used to create a coverage object.

2fill in blank

medium

Complete the code to stop coverage measurement and save the report.

Flask

cov.stop()
cov.[1]()

Drag options to blanks, or click blank then click option'

Astart

Breport

Cerase

Dsave

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'report' instead of 'save' before generating the report

Calling 'start' again instead of saving

After stopping coverage, save() writes the collected data to disk.

3fill in blank

hard

Fix the error in generating an HTML coverage report.

Flask

cov.[1](directory='coverage_html_report')

Drag options to blanks, or click blank then click option'

Ahtml_reporter

Bhtml_report

Chtml_reporter_dir

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'html_reporter' or similar incorrect method names

Passing wrong argument names

The correct method to generate an HTML report is html_report().

4fill in blank

hard

Fill both blanks to create a coverage report for specific files and omit tests.

Flask

cov = coverage.Coverage(source=[[1]], omit=[[2]])

Drag options to blanks, or click blank then click option'

A'app'

B'tests/*'

C'main.py'

D'docs/*'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'tests/*' as source instead of omit

Omitting the app folder instead of tests

The source parameter specifies the app folder, and omit excludes test files.

5fill in blank

hard

Fill all three blanks to correctly configure coverage to start, stop, and save in a Flask test setup.

Flask

cov = coverage.[1](branch=True)
cov.[2]()
# run tests
cov.[3]()

Drag options to blanks, or click blank then click option'

ACoverage

Bstart

Csave

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'save()' before stopping coverage

Not creating the coverage object properly

Create a coverage object with Coverage(), then start() before tests, and stop() after tests.

Practice

1. What is the main purpose of coverage reporting in a Flask application?

easy

A. To improve the speed of the Flask app

B. To deploy the Flask app to a server

C. To show which parts of the app are tested by your tests

D. To create a user interface for the app

Solution

1. Step 1: Understand coverage reporting

   Coverage reporting tracks which parts of your code are executed during tests.

2. Step 2: Identify its purpose in Flask

   It helps you see which parts of your Flask app have tests and which do not.

3. Final Answer:

   To show which parts of the app are tested by your tests -> Option C

4. Quick Check:

   Coverage reporting = shows tested parts [OK]

Hint: Coverage shows tested code parts, not speed or deployment [OK]

Common Mistakes:

• Confusing coverage with app speed optimization
• Thinking coverage deploys the app
• Assuming coverage creates UI

2. Which command correctly runs tests with coverage in a Flask project?

easy

A. pytest coverage run

B. coverage run -m pytest

C. flask coverage run

D. coverage test run

Solution

1. Step 1: Recall the coverage run syntax

   The correct command to run tests with coverage is 'coverage run -m pytest'.

2. Step 2: Check other options

   Other options mix commands incorrectly or use invalid syntax.

3. Final Answer:

   coverage run -m pytest -> Option B

4. Quick Check:

   Correct coverage test run command = coverage run -m pytest [OK]

Hint: Use 'coverage run -m pytest' to run tests with coverage [OK]

Common Mistakes:

• Swapping order of coverage and pytest
• Using 'flask' command with coverage incorrectly
• Typing 'coverage test run' which is invalid

3. Given you ran coverage run -m pytest successfully, which command shows a text summary of coverage results?

medium

A. coverage report

B. pytest --coverage

C. coverage html

D. flask coverage report

Solution

1. Step 1: Identify commands for coverage output

   'coverage report' shows a text summary in the terminal, while 'coverage html' creates a web page report.

2. Step 2: Eliminate incorrect options

   'pytest --coverage' is not a standard command, and 'flask coverage report' is invalid.

3. Final Answer:

   coverage report -> Option A

4. Quick Check:

   Text summary command = coverage report [OK]

Hint: Use 'coverage report' for text summary, 'coverage html' for web report [OK]

Common Mistakes:

• Confusing 'coverage html' with text output
• Using invalid commands like 'pytest --coverage'
• Trying 'flask coverage report' which doesn't exist

4. You ran coverage run -m pytest but coverage report shows 0% coverage. What is the likely cause?

medium

A. Tests did not execute any Flask app code

B. You forgot to install Flask

C. Coverage report command is misspelled

D. You ran coverage without pytest

Solution

1. Step 1: Understand 0% coverage meaning

   0% coverage means no code was executed during tests, so coverage tool found no lines run.

2. Step 2: Analyze possible causes

   If tests ran but did not call Flask app code, coverage stays zero. Missing Flask or misspelling commands would cause errors, not zero coverage.

3. Final Answer:

   Tests did not execute any Flask app code -> Option A

4. Quick Check:

   0% coverage = no app code run in tests [OK]

Hint: 0% means tests ran but didn't touch app code [OK]

Common Mistakes:

• Assuming 0% means Flask is not installed
• Thinking coverage report command typo causes 0%
• Believing running coverage without pytest causes 0%

5. You want to generate a detailed HTML coverage report for your Flask app after running tests. Which sequence of commands is correct?

hard

A. flask coverage run; coverage html; open html/index.html

B. pytest run coverage; coverage report; open index.html

C. coverage test run; coverage html; open coverage/index.html

D. coverage run -m pytest; coverage html; open htmlcov/index.html

Solution

1. Step 1: Run tests with coverage

   Use 'coverage run -m pytest' to run tests and collect coverage data.

2. Step 2: Generate HTML report and open it

   Run 'coverage html' to create the report in 'htmlcov' folder, then open 'htmlcov/index.html' to view it.

3. Step 3: Verify other options

   Other options use invalid commands or wrong paths for report files.

4. Final Answer:

   coverage run -m pytest; coverage html; open htmlcov/index.html -> Option D

5. Quick Check:

   Run tests, generate HTML, open htmlcov/index.html [OK]

Hint: Run tests, then 'coverage html', then open htmlcov/index.html [OK]

Common Mistakes:

• Using wrong command order or invalid commands
• Opening wrong file path for HTML report
• Confusing 'pytest run coverage' with correct syntax