Adding more documentation to tests

tests/README.md

-## Creating tests
+# Tests
 
-To create a test, just create a `.rb` file. It should finish normally if the test passed, and end with `exit 1` otherwise, preferably explaining why the test failed.
+## Why to run the tests
 
-## Running tests
+Running these tests will make sure that crew is working correctly, or explain the problem if it's not.
 
-Just run the `test_all` file. Running tests manually may not work!
+## When to run tests
+
+The tests can be used at any time to help with developing, but make sure to run them before submitting a Pull Request.
+
+## How to run the tests
+
+Execute `ruby test_all`. If all tests pass, it will print `All tests successful.`, otherwise it will show what went wrong.
+
+Running tests manually may not work!
+
+## Preparing new tests
+
+To prepare a new test, create a `.rb` file. It may use crew constants (created in `lib/const.rb`) and import packages (be sure to use `require_relative`).
+
+It should finish normally if the test passed, or finish with `exit 1` otherwise, preferably explaining why the test failed.
+All `.rb` files in this directory will automatically be run by the `all_tests` script.
+
+Here is a simple example of a test:
+
+```ruby
+# Makes sure buildessential package depends on gcc
+
+require_relative("../packages/buildessential")
+pkg = Object.const_get('Buildessential')
+if pkg.dependencies and pkg.dependencies.has_key?('gcc') then
+	puts "Everything works properly.".lightgreen
+else
+	puts "Buildessential should depend on gcc!".lightred
+end
+```

tests/no_cycles.rb

+# This test checks whether the packages create a dependency cycle.
+
 require 'find'
 require_relative '../lib/color'