When you're lost in the wilderness, with no or very little supplies, how is one to get food? It would be hard to actually catch something to eat, wouldn't it? So to actually get something inside your stomach, you turn to some leafy green plants.
Why? Because
a) they don't run away like an animal
b) you don't need to make a trap or other hunting device in order to kill it (sometimes you just need your bare hands)
But you don't know if the plants in your area are edible or not.
So to fix the problem, here is the edible plants test! (Whee)

Step 1: The VIRs (Very Important Rules)

When testing your plant, you want to make sure that even though you are doing the test, there are some rules to abide if you don't want to get sick.

1. Clean whatever you eat the best you can.
The plant might have animal leavings, germs or other contaminates on it.

2. Follow this test as to-the-book as possible as you might be paying the consequences, as whatever you are eating may kill you.
Also, in retrospect, some plants may be unresponsive to the test, but usually that is a small percentage.

3. Don't overeat on whatever you are eating. Your body might not be used to the species of plant you are eating. Also your body might not be used to all the fibre in the plant. It may cause digestion problems.

4. If you smell a peachy or almonds smell in your plant, leave it, as it is cyanide, a very strong poison to animals in general, including humans.

5. If an animal is eating a plant, doesn't mean you can.
Many animals have adapted to eating a specific plant, and sometimes the plant is poisonous. Some examples are monarch butterflies and poisonous milkweed, and koala bears and harmful eucalyptus leaves.

6. Never trust a mushroom, fungi, or anyone else in that plant family.
In the wild, safe fungi and mushroom can have many poisonous lookalikes. I would leave a mushroom alone, but if you are triple-checked sure that they are safe and you have eaten it before, then I suppose you can eat them.

Step 2: Separating the Plant

Only use one plant at a time, and while doing this test, don't eat anything else as it might affect the outcomes of the test.
First, separate the plant into four parts; root, leaves, berries, and the stem. Test each part of the plant one at a time, as parts of plants can be poisonous while others are not.

Step 3: The Rub Test

Find a sensitive place on your body, such as the inside of your wrist, your forearm, or inner thigh, and rub the plant onto the sensitive area.
Wait 45 minutes, while monitoring your body's reaction. Look for a rash, hives, dizziness, loss or shortness of breath, or puking. If you have these symptoms, do not eat the plant.

Step 4: The Lip Test

The next part of the test is to take a pinch of the plant and hold it against your lips for 10 minutes. Stop if you feel any itching or burning, and clean your face the best you can, and start over with another plant. If nothing happens, continue with the test.

Step 5: The Tongue Test

After the lip part of the test, put the pinch of the plant onto your tongue, and HOLD it there, and don't swallow for another 10 minutes. If anything feels wrong, spit the plant out. But if there isn't, continue with the test.

Step 6: The Chew Test

After holding the plant matter on your tongue, start chewing for about 5-10 minutes, again watching for any irritation or other symptoms.

Step 7: The Small Amount Swallow Test

If the chew section of the test does nothing, the next step is to swallow the plant. Next, you wait for 8 hours to see if you feel sick. If so, induce vomiting and drink as much water available.

Step 8: The Handful Swallow Test

If the pinch of plant matter went down well with no problems, move up to eating a handful of whatever plant you are eating. Again, wait 8 hours until you are sure that the plant is safe.

Kudos! You just learned how to test an edible or non edible plant!
I'm sorry it takes a little long, but it would be worth it if you actually were in the wild. Please try not to cut corners as it might end up risking your life.