Flags

Flags allow you to isolate and categorize coverage reports for different tests and features in your project. This is particularly helpful if:

1. You have multiple types of tests (e.g., unit, integration, frontend, backend, etc)

AND/OR

2. You're employing a monorepo setup where you'd like to encapsulate each project's test coverage independently.

Flags Example

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Video Walkthrough

To see the "flags" feature in action, you can also take a look at this video tutorial: https://about.codecov.io/product/feature/flags/

As a minimal example, consider a project called Monorepo X that has the following folder structure:

Monorepo X
    /front-end
    /back-end
    /mobile

We'll refer back to this Monorepo X example throughout the document.

Step 1: Flag Creation in Uploader

To apply a flag you must submit coverage reports with the -F flagname included in the upload command. (Note: remember, Codecov always recommends the Uploader in your CI)

It is important to note that for flagging to work, separate coverage reports must be uploaded and flagged per project in the mono repo. For example, in a CI run for the Monorepo X project example, assume that coverage for moduleA is written to

tests/front-end/output/coverage.xml

Then that report would be uploaded as follows:

./codecov -t <token> -f tests/front-end/output/coverage.xml -F moduleA

Now, your flag level coverage is being uploaded to Codecov.

# Ideal example of Flags matched to uploads in a CI pipeline

# Your Codecov Uploader approach here
# See more at https://docs.codecov.com/docs/codecov-uploader

# example running unittests only
py.test --cov=./ -k tests/unittests/
./codecov -c -F unittests

# example running integration tests only
py.test --cov=./ -k tests/integration/
./codecov -c -F integration

# example running ui tests only
npm test
./codecov -c -F ui

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Codecov will merge your reports for you

When using a tool like Flags, don't worry about merging your coverage reports before uploading to Codecov. Codecov will merge your coverage reports once you upload them.

One-to-One Relationship of Flags to Uploads

Specifying multiple flags for a single report upload can result in erroneous coverage unless the contents of that report fully encompass each flag.

For example, one report that contains coverage information for moduleA and moduleB, can be uploaded in a manner that is valid but technically incorrect:

# Not ideal example of many-to-one Flags to upload in a CI pipeline
 
./codecov -t <token> 
    -f coverage.xml -F front-end -F back-end -F mobile

This will apply the entire coverage of the report to both flags, resulting in incorrect coverage. Specifically, the front-end, back-end and mobile flags will display the coverage of the entire uploaded report, not just the subset of the report that happens to cover the files under their purview.

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Flags Must consist only of alphanumeric characters, '_', '-', or '.' and not exceed 45 characters

Flag names will be validated against the following regex. ^[\w\.\-]{1,45}$

Step 2: Flag Management in YAML

Once the uploader step is done (above), Flag-level coverage is being sent to Codecov, but, to unlock the full feature set of Codecov, you'll additionally have to add Flag Management to your repository-level YAML.

Here are just a few features unlocked by adding Flag definitions to your YAML.

1. Flags in PR Comments and Status Checks in your Github, Gitlab, Bitbucket instance
2. Overlay source code coverage in UI by Flag
3. Carryforward Flags for partial test runs
   Etc.

Two approaches to Flag Management

Recommended: Automatic Flag Management

Codecov's recommended approach to Flags is based on YAML settings under flag_management:

A. Relies on a set of default_rules: to automatically ingest uploaded flags, and manage Flags in an ongoing manner

B. If you have flags that don't fit the default_rules:, Universal Flag Settings allows for customization for any flags using individual_flags_rules:

Here is an example of default_rules: in the YAML

flag_management:
  default_rules: # the rules that will be followed for any flag added, generally
    carryforward: true
    statuses:
      - type: project
        target: auto
        threshold: 1%
      - type: patch
        target: 90%
  individual_flags: # exceptions to the default rules above, stated flag by flag
    - name: feature_1  #fill in your own flag name
      paths: 
      - src/feature_1  #fill in your own path. Note, accepts globs, not regexes
      carryforward: true
      statuses:
        - type: project
          target: 20%
        - type: patch
          target: 100%
    - name: feature_2 #fill in your own flag name
      paths: 
      - src/feature_2  #fill in your own path. Note, accepts globs, not regexes
      carryforward: true
      statuses:
      - type: project
        target: 20%
      - type: patch
        target: 100%

Changing your YAML? A reminder to always validate before you deploy https://api.codecov.io/validate

Advanced: Bespoke Flag Management

If you are going to use Bespoke Flag Management, you must add every flag individually to your YAML, which can be quite manual.

To generate a flag and individual coverage gates per project in the mono repo the codecov.yml can be structured as follows:

# Setting coverage targets per flag
coverage:
  status:
    project:
      default:
        target: 90% #overall project/ repo coverage
      front-end:
        target: 60%
        flags:    # this key tells Codecov to only use the coverage for these flags
          - front-end
      back-end:
        target: 100%
        flags:
          - back-end
      mobile:
        target: 80%
        flags:
          - mobile

# adding Flags to your `layout` configuration to show up in the PR comment
comment:
  layout: "reach, diff, flags, files"
  behavior: default
  require_changes: false  
  require_base: yes
  require_head: yes       
  branches: null

# New root YAML section = `flags:`
# This is where you would define every flag from your
# uploader, and update when new Flags added

flags:
  front-end:
    paths: #note, accepts globs, not regexes
      - src/front-end/code.js
    carryforward: false
  back-end:
    paths: #note, accepts globs, not regexes
      - src/back-end/api_code.py
    carryforward: true
  mobile:
    paths: #note, accepts globs, not regexes
      - src/new/mobile/app_code.java
    carryforward: true

This yaml configuration will fail a Pull Request if...

• ...the entire Monorepo project is below 90% covered (this is the default specification of the yaml above)
• ...the front-end coverage is less than 60%
• ...the back-end (API) coverage is less than 100%
• ...the mobile coverage is less than 80%

The front-end flag can be used for any number of reports (unit tests, integration tests, etc) by flagging each report with front-end. The reports will be merged and contribute to the project's total coverage and the total coverage of the files covered under the front-end flag.

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Remove old reports after uploading (optional)

Apply the -c argument to clear the workspace of all coverage reports before running you next set of tests.

Tracking Flag Coverage Over Time

The 'Flags' tab of your main repo navigation bar will allow you to visualize your historical flags data. This feature allows you to not just label portions of your code base, but use that labeling to track how that coverage is improving over time.

When you first click the tab you will need to "Enable Flag Analytics," this lets us know you'd like us to backfill your historical data. This process can sometimes take awhile, depending on the number of flags you have and how often you make a commit.

Once flag data has been backfilled you will be able to sort by flag name and filter to the date range of data you'd like to view. Forthcoming will be an ability to both search for and select only certain flags to view as well as other functionality to make this an easy to reference dashboard for your flag coverage. If you have feedback on this new feature, please let us know we'd love to hear what you think on this Github issue.

Additional Flag Use Cases

Carryforward Flags

Full documentation

If you do not test all of your repo code on each commit, Codecov uses a feature called Carryforward Flags to help only update coverage on tests that were run. Carryforward Flags is built on top of basic Flags. We use (and need) a full upload of all flags when carry forward is being used to initially set the coverage.

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Carryforward Flag Usage

It is highly recommended to read the full documentation on carryforward flags before using them in your project.

Carryforward Flags are used by appending your YAML with carryforward: true:

flags:
  ui:
    paths: #note, accepts globs, not regexes
      - ui_1.py
      - ui_2.py
    carryforward: true
  unit:
    paths:
      - unit_1.py
      - unit_2.py
    carryforward: true
  enterprise:
    paths:
      - ent_1.py
      - ent_2.py
    carryforward: false 
   # If no Carryfoward flag specified in YAML, the
   # default configuration is false.

Create custom notifications

Flags can be used to create custom notifications to your repository provider. This makes it easy to see per-flag coverage information alongside pull requests.

You can specify Flags in your Codecov Yaml for statuses and all notifications. Note that a flag must be specifically stated in the status: section of the YAML to have a custom notification associated.

coverage:
  status:
    project:
      default: off
      frontend:
        flags: 
          - frontend
      backend:
        target: 50%
        flags: 
          - backend
      api:
        target: 89%
        flags: 
          - api

flags:
  # filter the folder(s) you wish to measure by that flag
  backend:
    # only include files in the backend folder
    paths: #note, accepts globs, not regexes
      - app/backend/
  frontend:
    paths:
      - app/frontend/
  api:
    paths:
      - app/api/
  tests:
    paths:
      - tests/

Hide Builds (e.g., nightly builds)

Codecov provides a strategy to isolate specific builds from the master report while maintaining the report's integrity. When reports are not joined into the master report, they will be ignored for comparison, although they will remain accessible for source overlay, API, badges, and graphing.

A nightly build is an example of this feature. What follows is a Yaml configuration for a nightly build.

flags:
  nightly:
    joined: false

Now that we have configured the flag nightly to not join into the master report, let's upload a report flagged as nightly.

# Your Codecov Uploader approach here
# See more at https://docs.codecov.com/docs/codecov-uploader

./codecov -F nightly

By adding -F nightly we mark all the coverage report data for this build as nightly coverage data.