--- a/TestResource.st	Thu Oct 13 19:08:08 2016 +0200
+++ b/TestResource.st	Thu Oct 13 19:08:17 2016 +0200
@@ -16,6 +16,60 @@
 "
 !
 
+!TestResource class methodsFor:'documentation'!
+
+documentation
+"
+Normally a test will set up all the objects it needs and tear them down again after it has run.  
+This self-containedness makes a test more robust.  
+Use TestResources only for objects that are needed by several tests and that are too 'expensive' 
+(in time or otherwise) to recreate and destroy for each test.  
+
+A viable approach is to develop the code in MyTestCase's #setUp and #tearDown methods, 
+then at some point refactor the code into the #setUp and #tearDown of a TestResource 
+whose class is added to MyTestCase class>>resource method.
+
+TestResource uses the singleton pattern.  
+A TestResource class will set up a single instance of itself when first requested and tear it down again 
+at the end of TestSuite>>run (or TestCase>>run, >>debug and >>debugAsFailure).  
+Normally, a TestResource, once setUp, remains active during the running of all remaining tests 
+and is #reset after all tests have run.  
+
+For an exception, see subclass CompetingResource in SUnitResourcePatterns.  
+Users can choose to #reset a resource in the #tearDown of a test that alters it, 
+sacrificing the performance gain of having a single #setUp of the resource for the certainty 
+that other tests using it will not see the alterations.  
+
+Generally however, this should be the exception:  
+if you need to reset the resource for every test that uses it, 
+its code should just be part of your test's #setUp and #tearDown code.
+
+To use, create a subclass of TestResource and override the following:
+        - TestCase class>>resources, to return a collection including the TestResource class, 
+          for all test case classes that need it
+                * a TestCase' resources are set up in the order returned and torn down in the reverse order
+        - TestResource class>>resources, if the resource itself always needs some other resource 
+          to be present before it can set up
+                * a TestResource's resource are set up before it and torn down after it, and are set up in the order returned and torn down in the reverse order
+        - TestResource>>setUp and tearDown, to define initial and final behaviour (just like a test)
+        - TestResource>>isAvailable, to return true if it is and false if it isn't 
+          (the framework calls this after setUp);  ideally, this call should not change the resource' state 
+           - that should be done in setUp
+
+TestResource implements the singleton pattern in its class-side #isAvailable and #reset methods.  
+Do not override these when creating specific resources;  unless you are developing a whole new pattern of use, 
+it will always be correct to override instance-side #setUp, #tearDown and #isAvailable, 
+and dangerous to override class>>isAvailable, class>>isAlreadyAvailable and class>>reset.
+
+Generally, users do not code interactions with a test's resources during the running of a test.  
+Code that reads a resource' values while leaving its state strictly alone is safe enough.  
+A test must leave a resource in a clean state:  always use #reset if a test must protect 
+later-running tests from unsafe changes (and review whether in such a case a resource 
+is the right thing to use in the first place).
+
+See my superclass' comment for assertion and logging information.
+"
+! !
 
 !TestResource class methodsFor:'instance creation'!