make-test-builds-using-a-custom-flag.md

🏳️ make test builds using a custom flag

In mojo, it is possible to do it trough programming!

For serious testing, the assert functions provided mojo standard library should be used instead.

Note: testing is very important, and that code have not been tested. not ready for use

from sys.param_env import is_defined

alias testing = is_defined["testing"]()

#let's do colors for fun!
@always_inline
fn expect[message:StringLiteral ](cond:Bool):

    if cond: 
        #print in green
        print(chr(27),end='')
        print("[42m",end='')
    else: 
        #print in red
        print(chr(27),end='')
        print("[41m",end='')

    print(message,end='')
    
    #reset to default colors
    print(chr(27),end='')
    print("[0m")

fn main():
    @parameter
    if testing:
        print("this is a test build, don't use in production")

    @parameter
    if testing:
        expect["math check"](3==(1+2))
        #should print "math check in green"

pass testing "flag":

mojo build myfile.mojo -D testing

-D customised=1234 is also possible, see param_env