In order to keep test execution efficient when number of test cases grows, it is crucial to maintain corresponding metadata, which define some aspects of how the test coverage is executed.

This tool implements a flexible format for defining metadata in plain text files which can be stored close to the test code and structured in a hierarchical way with support for inheritance.

Although the proposal initially originated from user stories centered around test execution, the format is general and thus can be used in broader scenarios, e.g. test coverage mapping.

Using this approach it’s also possible to combine both test execution metadata and test coverage information. Thanks to elasticity and hierarchy it provides ability to organize data into well-sized text documents while preventing duplication.


These are essential corner stones for the design:

  • Text files under version control
  • Keep common uses cases simple
  • Use hierarchy to organize content
  • Prevent duplication where possible
  • Metadata close to the test code
  • Solution should be open source
  • Focus on essential use cases


Important user stories to be covered:

  • As a tester or developer I want to easy read and modify metadata and see history.
  • As a tester I want to select a subset of test cases for execution by specifying a tag.
  • As a tester I want to define a maximum time for a test case to run.
  • As a tester I want to specify which environment is relevant for testing.
  • As a user I want to easily define common metadata for multiple cases to simplify maintenance.
  • As a user I want to provide specific metadata for selected tests to complement common metadata.
  • As an individual tester and test contributor I want to execute specific single test case.
  • As an automation tool I need a metadata storage with good api, extensible, quick for reading.


These choices have been made:

  • Use git for version control and history of changes.
  • Yaml format easily readable for both machines and humans.


A dedicated file name extension fmf as an abbreviation of Flexible Metadata Format is used to easily find all metadata files on the filesystem:

  • smoke.fmf
  • main.fmf

Special file name main.fmf works similarly as index.html. It can be used to define the top level data for the directory.


The format does not define attribute naming in any way. This is up to individual projects. The only exception is the special name main which is reserved for main directory index.

Attribute namespacing can be introduced as needed to prevent collisions between similar attributes. For example:

  • test-description, requirement-description
  • test:description, requirement:description
  • test_description, requirement_description


Metadata form a tree where inheritance is applied. The tree root is defined by an .fmf directory (similarly as .git identifies top of the git repository). The .fmf directory contains at least a version file with a single integer number defining version of the format.


Individual tree nodes are identified by path from the metadata root directory plus optional hierarchy defined inside yaml files. For example, let’s have the metadata root defined in the wget directory. Below you can see node names for different files:

Location Name
wget/main.fmf /
wget/download/main.fmf /download
wget/download/smoke.fmf /download/smoke


Node names are unique across the metadata tree and thus can be used as identifiers for local referencing across the same tree. In order to reference remote fmf nodes from other trees a full fmf identifier is defined as a dictionary containing keys with the following meaning:

Git repository containing the metadata tree. Use any format acceptable by the git clone command. Optional, if no repository url is provided, local files will be used.
Branch, tag or commit specifying the desired git revision. This is used to perform a git checkout in the repository. If not provided, the default branch is used.
Path to the metadata tree root. Should be relative to the git repository root if url provided, absolute local filesystem path otherwise. Optional, by default . is used.
Node name as defined by the hierarchy in the metadata tree. Optional, by default the parent node / is used, which represents the whole metadata tree.

Here’s a full fmf identifier example:

ref: 0.10
path: /examples/wget
name: /download/test

Use default values for ref and path to reference the latest version of the smoke plan from the default branch:

name: /plans/smoke

If desired, it is also possible to write the identifier on a single line as supported by the yaml format:

{url: "", name: "/plans/smoke"}

Let’s freeze the stable test version by using a specific commit:

ref: f24ef3f
name: /tests/basic/filter

Reference a smoke plan from another metadata tree stored on the local filesystem:

path: /home/psss/git/tmt
name: /plans/smoke

Local reference across the same metadata tree is also supported:

name: /plans/smoke