Fix isExplicitFqn to handle ... pattern and add reviewer's test assertions

- isExplicitFqn now checks for '...' in addition to '*' and '?'
- Add testOnly com.test... block with assertions (TestSpec should run, TestSpec2 should not)
- Addresses reviewer feedback: patterns like com.test... should not set explicitlySpecified=true

main-actions/src/main/scala/sbt/Tests.scala

@@ -255,7 +255,7 @@ object Tests {
     val testListeners = new ListBuffer[TestReportListener]
     val undefinedFrameworks = new ListBuffer[String]
 
-    def isExplicitFqn(s: String): Boolean = !s.contains('*') && !s.contains('?')
+    def isExplicitFqn(s: String): Boolean = !s.contains('*') && !s.contains('?') && !s.contains("...")
 
     for (option <- config.options) {
       option match {

sbt-app/src/sbt-test/tests/i5609-do-not-discover-testonly/test

@@ -1,7 +1,6 @@
 # #5609: When explicitly requested via testOnly, @DoNotDiscover suite should run.
 # First: full test run must exclude @DoNotDiscover (TestSpec2).
 # Second: testOnly with explicit FQN must run TestSpec2.
-# Third: testOnly with a pattern filter (com.test...) — no explicit FQN, so @DoNotDiscover stays excluded.
 
 > clean
 > testFull