To activate Testing Cheats mode, during gamplay, press CTRL + SHIFT + C to bring up the console window. Enter "boolProp TestingCheatsEnabled true" to activate testing cheats mode. This is a very powerful cheat that enables many new things. In Create A Sim, after enabling this code, go into debugmode by pressing SHIFT + N before making a Sim. You now have the following new things in Create A Sim: clothing, skin tones, and some other options such as viewing the skinfilenames. During gamplay, after enabling this code, hold SHIFT and left click on a Sim to have lots of options, such as changing clothes, make your Sim fat or thin, set their aspiration level, etc. This code also can spawn some interesting items, such as the tombstone of L(ife) and D(eath), and family members.
Enable the "boolProp testingCheatsEnabled true" code, then go onto a different family. A code will appear at the top right hand corner. If you go onto the Sims' needs, you can click on each one and drag it up or down, whichever desired. You can also increase the skill points of your Sims in this way. This is useful if you want a promotion, if your Sim is depressed, if you are teaching a toddler to walk, etc. You can also hold [Shift] and click on a Sim. Click on "More", then "Spawn" and create the Tombstone of L and D. You can click on this, then "More" then "Make everyone here friends with me", which helps if you need friends to get promoted, or to complete an aspiration task.
Be cautious when using the "Testing cheats mode". Many glitches can occur, such as blocky/scattered picture, being unable to save, return to neighborhood, or quit. In rare cases if you use the code too much, you can lose the ability to travel to community lots. The car/taxi will drive offscreen, then immediately drive back.