Fix dcat tests for server mode and --plain flag handling

- Update dcat tests to use comma-separated file lists in server mode
- Fix basehandler.go to properly respect --plain flag for server messages
- Skip empty server messages when in plain mode
- Add separate expected output file for TestDCatColors server mode
- All dcat integration tests now pass in both serverless and server modes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/integrationtests-old/portnumber.go b/integrationtests-old/portnumber.go
new file mode 100644
index 0000000..94c2a11
--- /dev/null
+++ b/integrationtests-old/portnumber.go
@@ -0,0 +1,15 @@
+package integrationtests
+
+import "sync"
+
+var portNumberMutex sync.Mutex
+var currentPortNumber int = 4241
+
+// Go tests can run concurrently, so we need unique TCP port numbers for
+// each test.
+func getUniquePortNumber() int {
+	portNumberMutex.Lock()
+	defer portNumberMutex.Unlock()
+	currentPortNumber++
+	return currentPortNumber
+}