Features
Let’s demonstrate the features on a simple wget example with the following directory structure:
wget
├── download
├── protocols
│ ├── ftp
│ ├── http
│ └── https
├── recursion
└── smoke
Simple
The most common use cases super simple to read & write. Test metadata for a single test look like this:
description: Check basic download options
tester: Petr Šplíchal <psplicha@redhat.com>
tags: [Tier2, TierSecurity]
test: runtest.sh
time: 3 min
Hierarchy
Hierarchy is defined by directory structure (see example above) and
explicit nesting using attributes starting with /
. Defining
metadata for several tests in a single file is straightforward:
/download:
description: Check basic download options
tester: Petr Šplíchal <psplicha@redhat.com>
tags: [Tier2, TierSecurity]
test: runtest.sh
time: 3 min
/recursion:
description: Check recursive download options
tester: Petr Šplíchal <psplicha@redhat.com>
tags: [Tier2, TierSecurity]
test: runtest.sh
time: 20 min
Content above would be stored in wget/main.fmf
file.
Inheritance
Metadata is inherited from parent objects:
tester: Petr Šplíchal <psplicha@redhat.com>
tags: [Tier2, TierSecurity]
test: runtest.sh
/download:
description: Check basic download options
time: 3 min
/recursion:
description: Check recursive download options
time: 20 min
This nicely prevents unnecessary duplication. Redefining an attribute in a child object will by default overwrite value inherited from the parent.
If inheriting data from parent is not desired in particular node of the tree it is possible to disable it using the following directive:
/:
inherit: false
Merging
When inheriting values from the parent it is also possible to use
special attribute suffixes to merge child value with parent data.
Append a +
sign to the attribute name to add given value:
time: 1
/download:
time+: 3
This operation is possible only for attributes of the same type.
Exception MergeError
is raised if types are different. When
the +
suffix is applied on dictionaries update()
method is
used to merge content of given dictionary instead of replacing it.
The special suffix +<
can be used to prepend values instead of
appending them. This might be handy when adjusting lists:
steps:
- one
- two
- three
/complete:
steps+<:
- zero
In a similar way, appending a -
sign will reduce or remove
parent value from parent’s attribute (which has to be defined):
time-: 5
tags-: [Tier2]
desc-: details.*
vars-: [z]
Numbers are subtracted, list items are removed from the parent attribute, matching regular expressions are replaced by an empty string. For dictionaries it’s possible to provide list of keys which should be removed.
Substitution of current values can be done by appending a ~
suffix to the key name. The pattern and replacement parameters
need to be provided as values in the form of
<d>PATTERN<d>REPLACEMENT<d>
, where <d>
is delimiter which
can be any character however such character cannot be then used
within PATTERN and REPLACEMENT text as escaping isn’t supported.
This input can be either a string or list of strings.
The re.sub is used to do the substitution thus all features of
re.Pattern
can be used (named groups, back referencing…).
In the fmf file it is better to use single quotes '
as they do
not need such intensive escaping:
require~: ';^foo;foo-ng;'
recommend~:
- '/python2-/python3-/'
Remove parent value only if it matches regular expression is done
using the -~
suffix. If value matches any of provided
regular expressions it is removed. If the parent value is a
list, the matching item is removed from this list. If the parent
value is a string, the value is set to an empty string. If the
parent value is a dictionary, the matching key is removed. These
regular expressions can be just a single item or a list of
strings:
description-~: '.*'
require-~:
- 'python2.*'
Elasticity
Use a single file or scatter metadata across the hierarchy, whatever is more desired for the project.
File wget/main.fmf
:
tester: Petr Šplíchal <psplicha@redhat.com>
tags: [Tier2, TierSecurity]
test: runtest.sh
File wget/download/main.fmf
:
description: Check basic download options
time: 3 min
File: wget/recursion/main.fmf
:
description: Check recursive download options
time: 20 min
This allows reasonable structure for both small and large projects.
Scatter
Thanks to elasticity, metadata can be scattered across several
files. For example wget/download
metadata can be defined in
the following three files:
File wget/main.fmf
:
/download:
description: Check basic download options
test: runtest.sh
File wget/download.fmf
:
description: Check basic download options
test: runtest.sh
File wget/download/main.fmf
:
description: Check basic download options
test: runtest.sh
Parsing is done from top to bottom (in the order of examples above). Later/lower defined attributes replace values defined earlier/higher in the structure.
Leaves
When searching, key content is used to define which leaves
from the metadata tree will be selected. For example, every test
case to be executed must have the test
attribute defined,
every requirement to be considered for test coverage evaluation
must have the requirement
attribute defined. Otherwise object
data is used for inheritance only:
description: Check basic download options
test: runtest.sh
time: 3 min
The key content attributes are not supposed to be hard-coded in the Flexible Metadata Format but freely configurable. Multiple key content attributes (e.g. script & backend) could be used as well.
Select
Sometimes it is necessary to select node from the metadata tree even though it is not a leaf. For example, when virtual tests are created from a parent test but one wants to keep the parent available as a test as well. On the other hand, one might want to hide leaf node, instead of deleting it completely. To do so, one can set the directive:
/:
select: boolean
By default all leaves have it set to true
(such node is selected)
and branches have set it to false
(such node is not selected).
Virtual
Using a single test code for testing multiple scenarios can be easily implemented using leaves inheriting from the same parent:
description: Check basic download options
test: runtest.sh
/fast:
description: Check basic download options (quick smoke test)
environment: MODE=fast
tags: [Tier1]
time: 1 min
/full:
description: Check basic download options (full test set)
environment: MODE=full
tags: [Tier2]
time: 3 min
In this way we can efficiently create virtual test cases.
Adjust
It is possible to adjust attribute values based on the current Context, for example disable test if it’s not relevant for given environment:
enabled: true
adjust:
enabled: false
when: distro ~< fedora-33
because: the feature was added in Fedora 33
Note that this functionality reserves the following attributes for its usage:
- when
An optional condition to be evaluated in order to decide if the metadata should be merged. If not specified the adjust rule is applied as if it was set to
true
.- continue
By default, all provided rules are evaluated. When set to
false
, the first successful rule finishes the evaluation and the rest is ignored.- because
An optional comment with justification of the adjustment. Should be a plain string.
Name of the attribute which contains rules to be evaluated can be
arbitrary. In the example the default key adjust
is used.
Format
When investigating metadata using the fmf
command line tool,
object identifiers and all associated attributes are printed by
default, each on a separate line. It is also possible to use the
--format
option together with --value
options to generate
custom output. Python syntax for expansion using {}
is used to
place values as desired. For example:
fmf --format 'name: {0}, tester: {1}\n' \
--value 'name' --value 'data["tester"]'
Individual attribute values can be accessed through the data
dictionary, variable name
contains the object identifier and
root
is assigned to directory where metadata tree is rooted.
Python modules os
and os.path
as well as other python
functions are available and can be used for processing attribute
values as desired:
fmf --format '{}' --value 'os.dirname(data["path"])'