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Falderal Literate Test Format
This document describes the proposed Falderal Literate Test Format.
This document is a draft. It is nominally "version 0.12" because it
describes something that version 0.12 of
py-falderal mostly implements.
We will deign to note which sections of this document the current released
py-falderal implements, and which it does not. However,
this document is a work in progress, subject to change, and subject to get
out of sync with
py-falderal. It should not be considered to be
anything except a draft until it is described as "version 1.0".
A Falderal Literate Test Suite is a plain text file where some of the lines have special meaning to the Falderal Literate Test Format. Certain groupings of the lines defined by this format are intended to denote tests, while others denote pragmas which specify how those tests should be run. Outside of these groupings, lines have no meaning to the Falderal Literate Test Format other than that they are presumed to be mainly descriptive text.
The plain text file may also be formatted in some other format, such as Markdown, although this is not required.
A tool which claims to understand the Falderal Literate Test Format may choose to extract the tests from such a document, run them, and report which and how many of them passed or failed. That would be a typical application for this format. However, no tool is strictly required to do this with the tests found in a document; a tool may, for example, simply reformat the tests to produce an output file in a different format.
In the syntax templates below, words in
/slashes/ indicate a variable
rather than literal text.
Each grouping of lines which has special meaning to the Falderal Literate Test Format always begins with an indent of four (4) spaces from the leftmost column, preceded by non-indented text, and followed by either non-indented text or the end of the file. Such a grouping of lines is called a block.
There are two general formats to any block. In the first, "verbose" format, each indent of 4 spaces is followed immediately on that line by distinguished sequence of characters, called an introducer. The introducers which have meaning to the Falderal Literate Test Format are as follows:
->(hyphen, greater-than sign): pragma
|(vertical bar, space): test body text
+(plus sign, space): test input text
=(equals sign, space): expected output text
?(question mark, space): expected error text
If the same introducer occurs on multiple adjacent lines, the text after each introducer is concatenated to form one chunk of relevant text. This allows, for example, multi-line text to be given as the body, the input, or the expected output of a test.
There are some restrictions on the order in which introducers can sensibly occur in a block:
- Test body text should occur at the start of a block.
- Test body test may be optionally followed by test input text.
- The first test input text must be immediately preceded by test body text.
- Subsequent test input texts need not be preceded by a test body text; in this case, the previously-appearing test body text will be used again.
- Test body text must be followed by either test input text, expected output text, or expected error text, with no intervening text.
- Either expected output or error text must follow either test body text or test input text, with no intervening text.
See the sections for these introducers, below, for more details.
In the other, "freestyle" format, not all lines in a block require introducers. A freestyle format block is indentified as such if one or more of the final lines of the block begin with any of the following introducers:
=>: expected output text
==>: expected output text
===>: expected output text
?>: expected error text
??>: expected error text
???>: expected error text
In addition, the following introducers may be used to mark a section of test input text on the first of the final lines (but may not be used to end a block):
<=: test input text
<==: test input text
<===: test input text
If a block is identified as a freestyle block, all lines preceding the
first final line appearing with one of these introducers, are interpreted
as having no introducer at all (even if they begin with
| or some other
sequence already mentioned) and are used as the test body block.
Lines without introducers are called intervening text. Lines of intervening text are classified as either blank or non-blank. A line is blank if it contains no characters, or if it contains only whitespace. A group of non-blank lines is referred to as a paragraph.
The encoding pragma allows a Falderal file to specify what encoding is used for the characters in it. An implementation of Falderal is not expected to be able to handle any coding other than UTF-8, however, this pragma is included for the benefit of text editors and other tools, to indicate that the document is in fact in UTF-8 encoding.
-> encoding: UTF-8
The Functionality-definition pragma allows a Falderal file to describe ways in which a functionality being tested is implemented. It has the following syntax:
-> Functionality /functionality-name/ is implemented by /functionality-type/ /functionality-specifier/
functionality-type must at present be
shell command. The format of the
functionality-specifier differs according to the functionality-type.
The functionality-name is arbitrary text enclosed within double quotes,
which may be referenced in a later Tests-for pragma.
Note that the Functionality-definitions given in a Falderal file should not be considered exhaustive, or even requisite, by a tool. The tool may accept additional definitions of a functionality, referencing it by its name, from an external source such as the command line or a configuration file, and may be instructed to ignore certain Functionality-definitions in a Falderal file (if, for example, certain implementation are not currently available or of interest to the user.) Indeed, the functionality referred to by a functionality-name in a Tests-for pragma need not be defined by any Functionality-definition pragma in the same Falderal file, and this situation requires the functionality to be specified to the tool in some other manner.
For shell commands, the functionality-specifier is in the format
"command arg1 arg2 ... argn". Any line of legal Bourne shell syntax may
be used, so pipes, redirection, etc., are supported. Note that the double
quotation mark characters used to enclosed the command have meaning only to
the Falderal format — they are not part of the command, are not passed to the
shell, and do not require double quotation mark characters that are enclosed
by them to be escaped with a backslash.
Certain subsequences, called variables, if present in the command string, will be expanded before execution, and will alter how the command reads the text of the test and produces its output, to be compared with the expected output.
When a variable is expanded, it is Falderal's responsibility to escape any shell metacharacters that occur as part of the substitution text so that it appears to the shell as a single token, and cannot otherwise affect the meaning of the instantiated shell command. It is not necessary for a variable to be enclosed in any kind of quotes in the command line template. It is also not possible for the substitution text to e.g. expand to two arguments, or to form a pipe or redirection specifier, etc.
The exact method by which the Falderal implementation escapes or quotes the substitution text so that it appears unambiguously as a single argument is left up to the implementation.
%(test-body-file) will be replaced by the name of a file which
contains the text of the test body. This may be a temporary file created
solely for this purpose by the Falderal implementation.
%(test-body-text) will be replaced by the actual text of the
%(test-input-file) will be replaced by the name of a file which
contains the text of the test input. This may be a temporary file created
solely for this purpose by the Falderal implementation.
%(test-input-text) will be replaced by the actual text of the
If neither of the variables
in the command string, the test body text will be provided on the standard
input of the shell command.
If neither of the variables
in the command string, the test input text will be provided on the standard
input of the shell command.
If both the test body text and the test input text are slated to appear on the input of the shell command, then the behaviour is (presently) undefined.
%(output-file) will be replaced by the name of a file
(temporary file) to which the test results will be written. If it does
not appear in the command string, the output text will be read from
the standard output of the command.
How shell commands support error output is not yet standardized.
-> Functionality 'Prepending foo.txt' is implemented by shell command "cat foo.txt %(test-file) > %(output-file)"
The Tests-for pragma determines what functionality will be used to run all following tests, until the next Tests-for pragma. It has the following syntax:
-> Tests for /functionality-name/
The functionality-name refers to a functionality, which may be specified by a Functionality-definition pragma elsewhere in the Falderal file.
-> Tests for 'Reversing a string'
Test Body, Test Input and Expected Text
Each section of test body text may or may not be followed by a section of test input text; either way it must then be followed immediately by either and expected output section or expected error section.
Valid examples in the "verbose" format:
| thing to test = output to expect | thing to test ? error to expect | thing to test + input to give it = output to expect | thing to test + input to give it ? error to expect + different input to give the immediately previously defined test body ? different error to expect
Valid examples in the "freestyle" format:
thing to test => output to expect thing to test ==> output to expect thing to test ===> output to expect thing to test ?> error to expect thing to test ??> error to expect thing to test ???> error to expect thing to test <=== input to give it ===> output to expect thing to test <=== input to give it ???> error to expect
| thing to test
...needs an expectation.
+ input to give it = output to expect
...test input must be preceded by a test body, if this is the first test.
<=== input to give it ???> output to expect
...test input must be preceded by a test body always, in freestyle format.
? error to expect
...expectation must be preceded by either test input or test body.
A test body section may also be preceded by a paragraph of text; the intent of the Falderal Literate Test Format is that this text should describe the test, or rather, the aspect of the behaviour of the system that the test is meant to check. It is therefore reasonable that this text should be displayed along with the contents (test body text and expected output or error) of the test, in, for example, a test result report.
(This section is non-normative.)
Typically, a file in Falderal Literate Test Format will also be in Markdown format.
The format of the lines which comprise the Falderal Literate Test Format
was chosen to not conflict with many other common text formats (including
but not limited to Bird-style Literate Haskell, and Markdown); thus
literate test suites may be embedded in a wide variety of other formats.
However, there are inevitably some conflicts with some textual formats;
for example, when embedded in C code and many other languages, Falderal
entries should be preceded by
/* and followed by
*/, to ensure that
they are regarded as comments. Also, reStructuredText uses the
prefix to denote preformatted plain text.
The format of pragmas was chosen such that they could be read literately, and as such, a formatting tool could format them in the output document with little if any change.