Assertion functions

Description

The aim of these functions is to provide tools to test some other functions.

assert - Check that condition is true.
assert_checkerror - Check that an command raises the expected error.
assert_isapprox - Check that computed and expected values are approximately equal.
assert_isequal - Check that computed and expected values are equal.
assert_isfalse - Check that condition is false.
assert_istrue - Check that condition is true.