Skip to main content

A test framework for C projects.

Project description

buildstatus codecov

🦁 Nala

A test framework for C projects.

Based on narwhal and narmock.


  • Automatic test discovery
  • Use the same generic assertions everywhere
  • Assertion failures reported as diffs
  • Easy-to-use output capturing utilities
  • Amalgamated source file and header ready to drop in your project
  • Mocking support
  • Works well with errors reported by sanitizers
  • Test isolation with fork()
  • JSON test report


It’s recommended to install Nala with pip.

$ pip install nala

Alternatively, if mocking is not needed, you can download the amalgamated header and source files:

Drop the two files in your project, make sure nala.c is compiled and linked just like the other source files of your test program and you should be good to go.


Use nala init to create a test suite called foo.

$ nala init foo
Run 'make -C foo' to build and run the test suite!

The test suite is found in foo/main.c and contains two tests; the first uses all assertions and captures output, and the second mocks the time function.

#include <time.h>
#include "nala.h"
#include "nala_mocks.h"

    ASSERT_NE(1, 2);
    ASSERT_LT(1.0, 2.0);
    ASSERT_LE(1, 1);
    ASSERT_GT(2L, 1L);
    ASSERT_GE(1, 1);
    ASSERT_SUBSTRING("12345", "34");
    ASSERT_NOT_SUBSTRING("12345", "4567");
    ASSERT_MEMORY("abcd", "abcd", 5);
    ASSERT(1 == 1);

    CAPTURE_OUTPUT(output, errput) {
        fprintf(stderr, "err!\n");

    ASSERT_EQ(output, "std!\n");
    ASSERT_EQ(errput, "err!\n");


    ASSERT_EQ(time(NULL), 42);

Build and run the tests.

Compiler flags

Pass -no-pie -g -O0 -fsanitize=address to the compiler for better error reporting.

Read more about sanitizers here:

Debugging tips

Nala executes each test in its own process. This means that following the execution of a test with a debugger can be a bit tricky because debuggers like GDB can only follow a single process at a time.

If you’re using GDB, set a breakpoint at <test>_before_fork and then run the program until it stops at the breakpoint. Before continuing the program execution, tell GDB to follow the forked test process by setting follow-fork-mode to child.

All commands are shown below for the assertions test in the example above.

$ gdb ./a.out
(gdb) b assertions_before_fork
(gdb) r
(gdb) set follow-fork-mode child
(gdb) c


Generating mocks

The nala generate_mocks command finds the functions mocked in your code and generates nala_mocks.h, nala_mocks.c and nala_mocks.ld. The first two files declare and define mocks, while the last file contains linker flags.

Use --rename-parameters-file to rename function parameters, often useful when mocking standard library functions. If not given, Nala renames a few function parameters by default.

Use --no-rename-parameters not to rename any function parameters. Overrides --rename-parameters-file.

$ gcc -E *.c | nala generate_mocks

Nala requires source code to be expanded by the preprocessor. You can directly pipe the output of gcc -E to the command-line utility.

Mock API

The created mocks provides the following functions.

For all functions

<func>_mock(<params>, <res>)      - check parameters and return
<func>_mock_once(<params>, <res>) - check parameters and return once (per call)
<func>_mock_ignore_in(<res>)      - ignore parameters and return
<func>_mock_ignore_in_once(<res>) - ignore parameters and return once (per call)
<func>_mock_none()                - no calls allowed
<func>_mock_set_errno(int)        - errno on return
<func>_mock_implementation(*)     - replace implementation
<func>_mock_disable()             - call real implementation
<func>_mock_reset()               - mock reset
<func>_mock_assert_completed()    - completion checks
<func>_mock_set_callback(*)       - additional checks and/or actions

For selected function parameters

<func>_mock_ignore_<param>_in()               - ignore on input
<func>_mock_set_<param>_in(*, size_t)         - check on input
<func>_mock_set_<param>_in_assert(*)          - custom assert function on input
<func>_mock_set_<param>_in_pointer(*, size_t) - check pointer (the address) on input
<func>_mock_set_<param>_out(*, size_t)        - value on return
<func>_mock_set_<param>_out_copy(*)           - custom output copy function

For variadic functions

<func>_mock_ignore_va_arg_in_at(uint)          - ignore on input
<func>_mock_set_va_arg_in_at(uint, *, size_t)  - check on input
<func>_mock_set_va_arg_in_pointer_at(uint, *)  - check pointer on input
<func>_mock_set_va_arg_out_at(uint, *, size_t) - value on return


  • Structs and unions passed by value are ignored.
  • va_list parameters are ignored.


Remaining mocked calls

test_close failed:

  Location: nala_mocks.c:760
  Error:    Mocked close() called fewer times than expected. 2 call(s) missing.
  Remaining call(s):

    close(fd=1): return (-1)
    close(fd=4): return (0)

Failing mocked calls

test_close failed:

  Location: nala_mocks.c:760
  Error:    Mocked close(fd): 1 != 2

test_mount failed:

  Location: nala_mocks.c:760
  Error: Mocked mount(target): "b" != "c"

    -       target="b",
    +       target="c",
            data=00): return (0)

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for nala, version 0.48.0
Filename, size File type Python version Upload date Hashes
Filename, size nala-0.48.0-py2.py3-none-any.whl (33.2 kB) File type Wheel Python version py2.py3 Upload date Hashes View hashes
Filename, size nala-0.48.0.tar.gz (31.7 kB) File type Source Python version None Upload date Hashes View hashes

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN SignalFx SignalFx Supporter DigiCert DigiCert EV certificate StatusPage StatusPage Status page