gimp/libgimp/tests/README.md

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# Unit testing for libgimp
We should test every function in our released libraries and ensure they return
the correct data. This test infrastructure does this for the C library and the
Python 3 binding.
Every new test unit should be added both in C and Python 3.
## Procedure to add the C unit
C functions are tested in a real plug-in which is run by the unit test
infrastructure. Most of the boiler-plate code is contained in `c-test-header.c`
therefore you don't have to care about it.
All you must do is create a `gimp_c_test_run()` function with the following
template:
```C
static GimpValueArray *
gimp_c_test_run (GimpProcedure *procedure,
GimpRunMode run_mode,
GimpImage *image,
gint n_drawables,
GimpDrawable **drawables,
GimpProcedureConfig *config,
gpointer run_data)
{
/* Each test must be surrounded by GIMP_TEST_START() and GIMP_TEST_END()
* macros this way:
*/
GIMP_TEST_START("Test name for easy debugging")
/* Run some code and finish by an assert-like test. */
GIMP_TEST_END(testme > 0)
/* Do more tests as needed. */
/* Mandatorily end the function by this macro: */
GIMP_TEST_RETURN
}
```
This code must be in a file named only with alphanumeric letters and hyphens,
and prepended with `test-`, such as: `test-palette.c`.
The part between `test-` and `.c` must be added to the `tests` list in
`libgimp/tests/meson.build`.
## Procedure to add the Python 3 unit
Unlike C, the Python 3 API is not run as a standalone plug-in, but as Python
code directly interpreted through the `python-fu-eval` batch plug-in.
Simply add your code in a file named the same as the C file, but with `.py`
extension instead of `.c`.
The file must mandatorily start with a shebang: `#!/usr/bin/env python3`
For testing, use `gimp_assert()` as follows:
```py
#!/usr/bin/env python3
# Add your test code here.
# Then test that it succeeded with the assert-like test:
gimp_assert('Test name for easy debugging', testme > 0)
# Repeat with more tests as needed.
```