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This defines an API for writing test suites, to make it easy to portably test Scheme APIs, libaries, applications, and implementations. A test suite is a collection of test cases that execute in the context of a test-runner. This specifications also supports writing new test-runners, to allow customization of reporting and processing the result of running test suites.
There are other testing frameworks written in Scheme, including SchemeUnit. However SchemeUnit is not portable. It is also a bit on the verbose side. It would be useful to have a bridge between this framework and SchemeUnit so SchemeUnit tests could run under this framework and vice versa. However, that is not part of this specification.
There exists at least one Scheme wrapper providing a Scheme interface
standard JUnit API for Java.
It would be useful to have a bridge so that tests written using this
framework can run under a JUnit runner, and also that existing Scheme tests
run under the current framework.
However, that is not part of this specification.
We should have a testsuite for the testing framework. It should preferably be written using this specification, if that isn't too awkward. At the very least we need complete examples that exercise more of the API.
The implementation should be ported to other featureful Scheme implementations so they can make use of other than the lowest R5RS functionality.
Need to define error-type for
Need to nail down definition of test specifier - specifically how a value gets coerced to a specifier procedure.
The implementation could be polished a bit more.
The Scheme community needs a standard for writing test suites. Every SRFI or other library should come with a test suite. Such a test suite must be portable, without requiring any non-standard features, such as modules. The test suite implementation or "runner" need not be portable, but it is desirable that it be possible to write a portable basic implementation.
This API makes use of implicit dynamic state, including an
test runner. This makes the API convenient
and terse to use, but it may be a little less elegant and
than using explicit test objects, such as JUnit-style frameworks.
It is not claimed to follow either object-oriented or functional design
principles, but I hope it is useful and convenient to use and extend.
This proposal allows converting a Scheme source file to a test suite by just adding a few macros. You don't have to write the entire file in a new form, thus you don't have to re-ident it.
All names defined by the API start with the prefix
(Issue: Perhaps a colon prefix
testing: would be better.)
All function-like forms are defined as syntax. They may be implemented
as functions or macros or builtins. The reason for specifying them as
syntax is to allow specific tests to be skipped without evaluating sub-expressions, or for implementations
to add features such as printing line numbers or catching exceptions.
Let's start with a simple example. This is a complete self-contained test-suite.
;; Initialize and give a name to a simple testsuite. (test-begin "vec-test") (define v (make-vector 5 99)) ;; Require that an expression evaluate to true. (test-assert (vector? v)) ;; Test that an expression is eqv? to some other expression. (test-eqv (vector-ref v 2) 99) (vector-set! v 2 7) (test-eqv (vector-ref v 2) 7) ;; Finish the testsuite, and report results. (test-end "vec-test")
This testsuite could be saved in its own source file. Nothing else is needed: We do not require any top-level forms, so it is easy to wrap an existing program or test to this form, without adding indentation. It is also easy to add new tests, without having to name individual tests (though that is optional).
Test cases are executed in the context of a test runner,
which is a object that accumulates and reports test results.
This specification defines how to create and use custom test runners,
but implementations should also provide a default test runner.
It is suggested (but not required) that loading the above
file in a top-level environment will cause the
tests to be executed using an implementation-specified default test runner,
test-end will cause a summary to be displayed
in an implementation-specified manner.
Primitive test cases test that a given condition is true.
They may have a name.
The core test case form is
(test-assert [test-name] expression)
This evaluates the expression.
The test passes if the result
is true; if the result is false, a test failure is reported.
The test also fails if an exception is raised, assuming the implementation
has a way to catch exceptions.
How the failure is reported depends on the test runner environment.
The test-name is a string that names the test case.
It is used when reporting errors, and also when skipping tests,
as described below.
It is an error to invoke
if there is no current test runner.
The following forms may be more convenient than
(test-eqv [test-name] test-expr expected)
This is equivalent to:
(test-assert [test-name] (eqv? test-expr expected))
are shorthand for
test-assert combined with
Here is a simple example:
(define (mean x y) (/ (+ x y) 2.0)) (test-eqv (mean 3 5) 4)
We need a way to specify that evaluation should fail. This are tests that errors are detected.
(test-error [[test-name] error-type] test-expr)
Evaluating test-expr is expected to signal an error. The kind of error is indicated by error-type.
Issue: What is error-type? Perhaps a condition type or the associated predicate, in the SRFI-35 sense?
If the error-type is left out, or it is
#t, it means "some kind of unspecified error should be signaled".
(test-error #t (vector-ref #(1 2) 9))
An implementation that cannot catch exceptions should skip
A test group is a named sequence of forms containing testcases, expressions, and definitions. Entering a group sets the test group name; leaving a group restores the previous group name. These are dynamic (run-time) operations, and a group has no other effect or identity. Test groups are informal groupings: they are neither Scheme values, nor are they syntactic forms.
A test group may contain nested inner test groups. The test group path is a list of the currently-active (entered) test group names, oldest (outermost) first.
test-begin enters a new test group.
The suite-name becomes the current test group name,
and is added to the end of the test group path.
Portable test suites should use a sting literal for suite-name;
the effect of expressions or other kinds of literals is unspecified.
Rationale: In some ways using symbols would be preferable. However, we want human-readable names, and standard Scheme does not provide a way to include spaces or mixed-case text in literal symbols.
Additionally, if there is no currently executing test runner, one is installed in an implementation-defined manner.
(test-end [suite-name] [count])
test-end leaves the current test group.
An error is reported if the suite-name does not
match the current test group name. If it does match an earlier
name in the test group path, intervening groups are left.
The optional count must match the number of
test-cases executed since the matching
(Nested test groups count as a single test case for this count.)
This extra test may be useful to catch cases where a test doesn't
get executed because of some unexpected error.
Additionally, if the matching
installed a new test-runner, then the
will de-install it, after reporting the accumulated test
results in an implementation-defined manner.
(test-group suite-name decl-or-expr ...)
(if (not (test-to-skip% suite-name)) (dynamic-wind (lambda () (test-begin suite-name)) (lambda () decl-or-expr ...) (lambda () (test-end suite-name))))
This is usually equivalent to executing the decl-or-exprs
within the named test group. However, the entire group is skipped
if it matched an active
test-skip (see later).
test-end is executed in case of an exception.
Issue: In the case of an exception, should we actually catch it,
and proceed following the
test-group, or should we
use a separate form for catching errors?
(test-group-with-cleanup suite-name decl-or-expr ... cleanup-form)
(test-group-with-cleanup "test-file" (define f (open-output-file "log")) (do-a-bunch-of-tests f) (close-output-port f))
Sometimes we want to only run certain tests, or we know that certain tests are expected to fail. A test specifier is one-argument function that takes a test-runner and returns a boolean. The specifier may be run before a test is performed, and the result may control whether the test is executed. For convenience, a specifier may also be a non-procedure value, which is coerced to a specifier procedure as needs to be decided.
The resulting specifier matches if the current test name (as returned by
(test-match-nth n [count])
This evaluates to a stateful predicate: A counter keeps track of how many times it has been called. The predicate matches the n'th time it is called (where
1 is the first time), and
(- count 1) times,
where count defaults to
(test-match-any specifier ...)
The resulting specifier matches if any specifier matches.
(test-match-all specifier ...)
The resulting specifier matches if each specifier matches.
In some cases you may want to skip a test.
test-skip adds the
to the set of currently active skip-specifiers.
Before each test (or
the set of active skip-specifiers are applied to the active test-runner.
If any specifier matches, then the test is skipped.
For convenience, if the specifier is a string that
is syntactic sugar for
(test-skip "test-b") (test-assert "test-a") ;; executed (test-assert "test-b") ;; skipped
Any skip specifiers introduced by a
are removed by a following non-nested
(test-begin "group1") (test-skip "test-a") (test-assert "test-a") ;; skipped (test-end "group1) ;; Undoes the prior test-skip (test-assert "test-a") ;; executed
Sometimes you know a test case will fail, but you don't have time to or can't fix it. Maybe a certain feature only works on certain platforms. However, you want the test-case to be there to remind you to fix it. You want to note that such tests are expected to fail.
Matching tests (where matching is defined as in
are expected to fail. This only affects test reporting,
not test execution.
A test-runner is an object that runs a test-suite, and manages the state. The test group path, and the sets skip and expected-fail specifiers are part of the test-runner. A test-runner will also typically accumulate statistics about executed tests,
Get or set the current test-runner. If an implementation supports parameter objects (as in SRFI-39), then
test-runner-current can be a parameter object.
test-runner-current may be implemented
as a macro or function
that uses a fluid or thread-local variable, or a plain global variable.
Creates a new simple test-runner, that prints errors and a summary on the standard output port.
Creates a new test-runner, that does nothing with the test results. This is mainly meant for extending when writing a custom runner.
Implementations may provide other test-runners, perhaps
Create a new test-runner. Equivalent to
Get or set the current test-runner factory. A factory is a zero-argument function that creates a new test-runner. The default value is
but implementations may provide a way to override the default.
test-runner-current, this may be a parameter object,
or use a per-thread, fluid, or global variable.
(test-apply [runner] specifier ... procedure)
Calls procedure with no arguments using the specified
runner as the current test-runner.
If runner is omitted,
(test-runner-current) is used.
(If there is no current runner, one is created as in
If one or more specifiers are listed then only tests matching
the specifiers are executed. A specifier has the same form
as one used for
test-skip. A test is executed
if it matches any of the specifiers in the
test-apply and does not match any
(test-with-runner runner decl-or-expr ...)
Executes each decl-or-expr in order in a context where the current test-runner is runner.
This section can be ignored if you just want to write test-cases.
A test-result is an association list that contains various information about the result of a test. Some associations are standard; implementations can add more.
test-kind association return one of the following symbols:
If an impementation can pass the source location (filename and line)
to the test routines, they should use the associations
Examples needed. Also more standard associations.
The following functions are for accessing the components of a test-runner. They would normally only be used to write a new test-runner or a match-predicate.
Returns the number of tests that passed, and were expected to pass.
Returns the number of tests that failed, but were expected to pass.
Returns the number of tests that passed, but were expected to fail.
Returns the number of tests that failed, and were expected to pass.
Returns the number of tests or test groups that were skipped.
Returns the name of the current test or test group, as a string. During execution of
test-begin this is the name of the
test group; during the execution of an actual test, this is the name
of the test-case.
If no name was specified, the name is the empty string.
(test-runner-aux-value! runner on-test)
Get or set the
aux-value field of a test-runner.
This field is not used by this API or the
test-runner, but may be used by custom test-runners to store extra state.
(test-runner-on-test! runner on-test)
Gets or sets the procedure that is run after each test to report the results. The procedure takes two parameters: a test-runner, and an association list giving information about the test. (Need more specifics on this!) Typically, this procedure may be emit terse or no output if the test succeeded or was skipped, and emit more detailed output if the test failed. The initial value is
test-on-test-simple which writes
to the standard output (fill this in later).
(test-runner-on-final! runner on-final)
Gets or sets the procedure that is run at the very end to report the results. The procedure takes one parameter (a test-runner) and typically displays a summary (count) of the tests. The initial value is
test-on-final-simple which writes
to the standard output port the rumber of tests of the various kinds.
Resets the state of the runner to its initial state.
This is an example of a simple custom test-runner. Loading this program before running a test-suite will install it as the default test runner.
(define (my-simple-runner filename) (let ((runner (test-runner-null)) (port (open-output-file filename)) (num-passed 0) (num-failed 0)) (test-runner-on-test! runner (lambda (runner result) (case (cdr (assq 'result-kind result)) ((pass xpass) (set! num-passed (+ num-passed 1))) ((fail xfail) (set! num-failed (+ num-failed 1))) (else #t)))) (test-runner-on-final! runner (lambda (runner) (format port "Passing tests: ~d.~%Failing tests: ~d.~%" num-passed num-failed) (close-output-port port))) runner)) (test-runner-factory (lambda () (my-simple-runner "/tmp/my-test.log")))
The test implementation uses
to select different code depending on certain SRFI names (
or implementations (
It should otherwise be portable to any R5RS implementation.
(It has been tested on Kawa, MzScheme, and Chez Scheme.
So far only Kawa makes use of non-R5RS features; patches welcomed.)
The implementation is neither finished nor debugged, but I hope ready for people to experiment with.testing.scm
Of course we need a test suite for the testing framework testself.
For that we need a meta-lever test-runner.
test-with-runner should be helpful.
Copyright (C) Per Bothner (2005)
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