Coverage reporting in Django - Step-by-Step Execution

Concept Flow - Coverage reporting

Write Django Tests

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Run Tests with Coverage

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Coverage Tool Tracks Lines

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Generate Coverage Report

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Review Report for Missing Coverage

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Improve Tests and Repeat

This flow shows how coverage reporting works in Django: write tests, run them with coverage tracking, generate a report, and improve tests based on it.

Execution Sample

Django

coverage run manage.py test
coverage report
coverage html

Run Django tests with coverage tracking, then show a text report and generate an HTML report.

Execution Table

Step	Action	Coverage Tool Behavior	Output
1	Run 'coverage run manage.py test'	Starts coverage tracking, runs all Django tests	Tests run, coverage data collected
2	Tests execute lines in views.py	Coverage tool marks executed lines as covered	Coverage data updated for views.py
3	Tests execute lines in models.py	Coverage tool marks executed lines as covered	Coverage data updated for models.py
4	Tests skip some lines in utils.py	Coverage tool marks those lines as missing coverage	Coverage data shows missing lines in utils.py
5	Run 'coverage report'	Summarizes coverage data in terminal	Text report shows % covered per file
6	Run 'coverage html'	Generates detailed HTML report with line highlights	HTML files created in 'htmlcov' folder
7	Open 'htmlcov/index.html'	View detailed coverage with green/red lines	Visual report shows covered and missed lines
8	Review report and add tests for missed lines	Coverage data will improve on next run	Cycle repeats for better coverage

💡 Coverage report generated and reviewed; testing cycle can repeat to improve coverage.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
coverage_data	empty	views.py lines covered	models.py lines covered	utils.py missing lines noted	complete coverage data with misses

Key Moments - 2 Insights

Why do some lines show as missing coverage even though tests run?

Because those lines were not executed by any test, as shown in execution_table row 4 where utils.py lines are skipped.

What does the 'coverage html' command do differently than 'coverage report'?

'coverage html' creates a detailed visual report with colored lines, while 'coverage report' shows a summary in the terminal, as seen in rows 5 and 6.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 4?

A All lines are covered by tests

B Coverage tool marks some lines as missing coverage

C Tests fail to run

D HTML report is generated

💡 Hint

Check the 'Coverage Tool Behavior' column at step 4 in the execution_table.

At which step is the HTML coverage report created?

A Step 2

B Step 3

C Step 6

D Step 8

💡 Hint

Look for 'Generates detailed HTML report' in the execution_table.

If you add tests for missed lines, what will happen to coverage_data after rerunning tests?

A Coverage data will show more lines covered

B Coverage data will be empty

C Coverage data will show fewer lines covered

D Coverage data will not change

💡 Hint

Refer to the last row in execution_table about improving coverage by adding tests.

Concept Snapshot

Coverage Reporting in Django:
- Run tests with 'coverage run manage.py test'
- Use 'coverage report' for terminal summary
- Use 'coverage html' for detailed visual report
- Review missing lines and add tests
- Repeat to improve coverage percentage

Full Transcript

Coverage reporting in Django helps you see which parts of your code are tested. You run your tests with coverage tracking using 'coverage run manage.py test'. The coverage tool watches which lines run during tests. Then you generate a report with 'coverage report' to see a summary in the terminal or 'coverage html' to get a detailed colored report in your browser. This report shows green lines for covered code and red lines for missed code. You can then add tests for missed lines and run coverage again to improve your test coverage. This cycle helps you write better tested Django apps.