add alternative way to filter tests. It may be useful for 3rd party plugins

Detailed-Topics/Testing.md

@@ -141,10 +141,18 @@ parallelExecution in Test := false
 
 If you want to only run test classes whose name ends with "Test", use `Tests.Filter`:
 
-```
+```scala
 testOptions in Test := Seq(Tests.Filter(s => s.endsWith("Test")))
 ```
+or if you want remove other tests from `detected-tests` for some reason:
 
+```scala
+definedTests in Test <<= (definedTests in Test) {
+  (tests) =>
+    def filter(tests: Seq[TestDefinition]) = tests.filter(t => t.name.endsWith("Test"))
+    tests map filter
+}
+```
 ## Forking tests
 
 In version 0.12 the facility to run tests in a separate JVM has been added. The setting