bdd-for-c

The bdd-for-c library is a BDD test framework for the C language.

Quick Start

To start, simply download the framework header file which can be easily done with curl on Linux, MacOS, and BSD Unix:

curl -O https://raw.githubusercontent.com/grassator/bdd-for-c/master/bdd-for-c.h

Next, create a spec file, named something appropriate like strncmp_spec.c if testing the strncmp function. Add some tests and include the framework header, like the following:

#include <string.h>
#include "bdd-for-c.h"

spec("strncmp") {
    static const char *test_string = "foo";

    it("should return 0 when strings are equal") {
        check(strncmp(test_string, test_string, 12) == 0);
        check(strncmp(test_string, "foo", 12) == 0);
    }

    it("should work for empty strings") {
        check(strncmp("", "", 12) == 0);
    }

    it("should return non-0 when strings are not equal") {
        check(strncmp("foo", "bar", 12) != 0);
        check(strncmp("foo", "foobar", 12) != 0);
    }

    it("should return 0 when strings match up to specified length") {
        check(strncmp("foobar", "foobaz", 3) == 0);
    }
}

Assuming you have a C compiler like Clang or GCC set up and ready to go, just type in the following commands to compile and run the test:

cc strncmp_spec.c -o strncmp_spec
./strncmp_spec

You should then see test output similar to the following:

strncmp
  should return 0 when strings are equal (OK)
  should work for empty strings (OK)
  should return non-0 when strings are not equal (OK)
  should return 0 when strings match up to specified length (OK)

Dependencies

On *nix systems, bdd-for-c depends on the following libraries:

libncurses 5.x
libbsd

On Ubuntu-like (Debian) distributions you can install them via:

sudo apt-get install libncurses5-dev libbsd-dev

Project Motivation and Development Philosophy

In order for testing to be truly useful, it needs to be easy to set up and use, but also scalable for large projects. The tests should be very readable but, ideally, have the same look-and-feel as the host language. The framework's test output should be easy to read for both humans and machines. Finally, if it's C, the framework should only rely on ANSI/ISO-C99 features.

Unfortunately, all of the existing frameworks inspected before starting this project lack one or more of those requirements, with the most common problem being BASIC-style BEGIN / END delimiters for a test, like in the CSpec framework. The issue with BEGIN / END delimiters is not just that it "doesn't look like C", but also that it imposes a different typing flow and screws up auto-completion support for IDEs and programming text editors.

The bdd-for-c framework currently exclusively targets the model of "one spec, one executable", as this model provides the fastest compile times (given a correctly structured project). This also makes mocking much easier.

Handling State and Fixtures

If you need to set up some state once before all the tests, or before each of the tests, bdd-for-c supports special before and before_each statements, and their counterparts after and after_each. As a bonus, you can define as many before, after, before_each and after_each statements in any order as you want, as long as they are on the same level as the corresponding it statement.

The only caveat with handling state is that, if you want to create some test-local variables, you need to mark them as static. Otherwise, the changes done before and before_each will not persist to the test itself, as each of the tests and these setup / teardown functions are implemented as separate function calls.

Here's how it all fits together:

#include <stdio.h>
#include "bdd-for-c.h"

spec("some feature") {

    static int test_count;
    static int tests_failed;

    after() {
        printf("  All done!\n");
    }

    after() {
        printf("%i tests run. %i failed.\n", test_count, tests_failed);
    }

    before() {
        test_count = 0;
        tests_failed = 0;
    }

    before() {
        printf("  Starting the tests...\n\n");
    }

    before_each() {
        ++test_count;
        ++tests_failed;
    }

    after_each() {
        --tests_failed;
    }

    describe("broken math") {
        it("should not be equal") {
            check(3 + 2 != 6, "this is indeed broken!");
        }
    }

    context("when everything is right") {
        it("should work") {
            check(3 + 3 == 6);
        }
    }
}

Output Colorization

By default, if the terminal correctly reports its color printing ability and the application is run in the interactive mode (from terminal), then the output is going to be colorized.

To disable this mode, simply add a define statement before you include the bdd-for-c.h file:

#define BDD_USE_COLOR 0
#include "bdd-for-c.h"

Note to CLion users: To get colored output when running tests from the IDE, you need to add TERM=xterm-256color to the Environment Variables field of your build configuration.

Support for TAP

The bdd-for-c library supports the test anything protocol, or TAP, which formats output to be easily readable by programs. This allows easier integration with continuous integration systems as well as the aggregation of output from multiple executables that use bdd-for-c.

To switch to TAP output mode you can add a define statement before including the framework:

#define BDD_USE_TAP 1
#include "bdd-for-c.h"

You may also add an environment variable when you run a test, instead:

BDD_USE_TAP=1 ./strncmp_spec

Available Statements

The bdd-for-c framework uses macros to introduce several new statements to the C language that are similar to the built-in statements, such as if.

These macros are implemented to be syntactically identical to the built-in statements. Among other things, this means that for the statements that expect a body, the body can be empty (by terminating it with a semicolon), contain one statement, or contain a code block (a list of statements):

#include "bdd-for-c.h"

spec('statements') {
    it("should not do anything");
    it("should be in short form") check(1 + 1 == 2);
    it("should have a code block") {
        check(1 + 1 == 2);
    }
}

As with the built-in statements, you have to maintain a certain structure, described where appropriate in the subsections below.

spec

The spec statement must be a top-level statement and there must be exactly one spec statement in the test executable. Using more than one will result in a compilation error.

Use spec("some functionality") to group a set of expectations and setup/teardown code together, and to give the unit a name (in this case "some functionality"). This will be used for test reporting.

it

You must include it statements directly inside a spec, describe, or context statement. Each it statement expects a string argument, typically starting with "should", used as a human readable explanation for the test, and used in reporting: it("should behave in some manner").

The it statement is a basic structural block of the spec and is used to ensure a particular expectation, validated using check statements (described below).

fit / it_only

This is is similar to it, but switches test runner into a mode where it will only run tests defined with fit / it_only.

xit / it_skip

This is is similar to it, but skips this particular test. Unlike source editing options of disabling the tests like commenting out or if (0) you still get in an entry in the output with the name of the test marked as (SKIP).

describe

A describe statement must be included directly inside a spec or context statement, or within another describe statement. It is used to group it statements together, usually based on the fact that they belong to the same unit of program functionality.

context

A context statement is functionally identical to describe, and should be used when it better conveys the topic of a group of tests. It is usually used to group describe statements based on the fact they depend on the same program state, providing a way to easily set up the same program state for several test conditions.

NOTE: Because context is a quite common global variable in C applications, it is possible to not expose the context implementation in bdd-for-c by setting a flag before including the bdd-for-c library:

#define BDD_NO_CONTEXT_KEYWORD 1
#include "bdd-for-c.h"

check

A check statement is used to check "truthfulness" of a given expression. In case of failure, it terminates the current spec block and reports an error. These statements must be placed inside of it statements, either as direct or indirect children:

#include "bdd-for-c.h"

spec("natural number") {
    it("should be non-negative") {
        for (int i = 0; i < 10; ++i) {
            check(i > 0);
        }
    }
}

By default, a check statement uses the provided expression for error reporting, so, if you run the code above, you will see the following line:

Check failed: i > 0

Depending on your variable naming, as in this example, test output can be unhelpful for figuring out the cause of the failure. To remedy this problem, you can provide a formatter and additional parameters in the same manner as with printf:

check(i > 0, "a natural number %i must be greater than 0", i);

This can provide much more informative output:

Check failed: a natural number 0 must be greater than 0

Due to limitations in the current implementation, the number of parameters to check is limited to 10.

While check statements are mostly useful inside of it statements, you can use them in setup and teardown statements (before, after, before_each, after_each) to validate some pre- or post-conditions as well.

before

A before statement, if needed, can be included directly inside a spec, describe, or context statement. It runs once before all of the it statements in the group/spec and can be useful to set up some state. You can use as many before statements as necessary.

after

An after statement, if needed, can be included directly inside a spec, describe, or context statement. It runs once after all it statements in the group and can be useful to tear down some state. You can use as many after statements as necessary.

before_each

A before_each statement, if needed, can be included directly inside a spec, describe, or context statement. It runs before each it statement and can be useful to set up some state. You can use as many before_each statements as necessary.

after_each

An after_each statement, if needed, can be included directly inside a spec, describe, or context statement. It runs after each it statement and can be useful to tear down some state. You can use as many after_each statements as necessary.

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

grassator/bdd-for-c

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