Correct three texts a tester reads: 8.20.2a's IIN check, 10.4.4 step 12's sequence, and the capture adapter option

src/main/scala/io/stepfunc/dnp3c/conformance/api/options/ChannelOptions.scala

@@ -13,7 +13,12 @@ object ChannelOptions extends OptionGroup {
   val host: StringOption = OptionTypes.string(this, "device.address", "127.0.0.1", "IP address of the DUT")
   private val port = OptionTypes.integer(this, "device.port", 20000, "IP port of the DUT", Some(1), Some(65535))
   private val captureNIC =
-    OptionTypes.string(this, "capture.adapter", "", "IP address of the network adapter on which to capture pcaps")
+    OptionTypes.string(
+      this,
+      "capture.adapter",
+      "",
+      "Address of the network adapter on which to capture pcaps, as -adapters prints it, e.g. /192.168.1.10; empty for no capture"
+    )
 
   def prefix: String = "tcp"
   def description: String = "TCP options"

src/main/scala/io/stepfunc/dnp3c/conformance/application/pcap/PacketCapture.scala

@@ -40,7 +40,8 @@ object PacketCapture {
 
     val interface: PcapNetworkInterface = {
       interfaces.find(d => matches(nic, d.getAddresses.asScala.toList)).getOrElse {
-        throw new Exception("Unable to find network adapter: " + nic)
+        throw new Exception(
+          s"Unable to find network adapter: $nic (give its address as -adapters prints it, e.g. /192.168.1.10)")
       }
     }
 

src/main/scala/io/stepfunc/dnp3c/conformance/common/Validations.scala

@@ -50,8 +50,12 @@ object Validations {
     IIN((IIN.errors.lsb & ~allowed.lsb).toByte, (IIN.errors.msb & ~allowed.msb).toByte)
 
   // 3.1r1's Null Error Response: no objects, and at least one of the error bits allowed, but no other error bit
-  def isNullErrorResponse(allowed: IIN): MessageValidation =
-    isEmpty && containingAnyOf(allowed) && without(errorsExcept(allowed))
+  def isNullErrorResponse(allowed: IIN): MessageValidation = {
+    val others = errorsExcept(allowed)
+    // with every error bit allowed there's nothing to rule out, and an empty check would print as "IIN()"
+    if (others.lsb == 0 && others.msb == 0) isEmpty && containingAnyOf(allowed)
+    else isEmpty && containingAnyOf(allowed) && without(others)
+  }
 
   // Null Response, or an Error Response whose error bits are all in `allowed` (an Error Response may contain data)
   def isNullOrErrorResponse(allowed: IIN): MessageValidation = new MessageValidation {

src/main/scala/io/stepfunc/dnp3c/conformance/v31r1/OutputEvents.scala

@@ -474,7 +474,9 @@ object OutputEvents {
           driver.writeMessage(Message.request(s, AppFunction.select, List(header)))
         },
         12 --> new TestStep {
-          def description: List[Comment] = expectSingleResponse(Sequence.zero, echoes(header)).description
+          // the sequence is the Select's, known only when it runs
+          def description: List[Comment] =
+            "Read a single fragment response" :: expectSingleResponse(Sequence.zero, echoes(header)).description.tail
           def run(driver: TestDriver): List[DeferredCheck] = expectSingleResponse(s, echoes(header)).run(driver)
         },
         13 --> delay(timeoutMs + 1000),

src/main/scala/io/stepfunc/dnp3c/conformance/v31r1/PointRanges.scala

@@ -136,7 +136,7 @@ object PointRanges {
       Option.when(t.escapeStep)(OptionCondition(SupportOptions.rangeReads)).toList)*)
 
   // a level 1 or 2 device without range reads answers with IIN2.0, 2.1 or 2.2
-  private val unsupported = isEmpty && containingAnyOf(IIN.errors)
+  private val unsupported = isNullErrorResponse(IIN.errors)
 
   /** x.2: a range of points the DUT has gets those points, and only those */
   def validRequest(t: RangedPoints): ProcedureDefinition = new ProcedureDefinition {

src/main/scala/io/stepfunc/dnp3c/conformance/v31r1/StaticInputs.scala

@@ -61,7 +61,7 @@ object StaticInputs {
     }
 
     private def declined(seq: Sequence, variation: Variation): TestStep = new TestStep {
-      private val check = isEmpty && containingAnyOf(IIN.errors)
+      private val check = isNullErrorResponse(IIN.errors)
       def description: List[Comment] = check.description :+
         Comment("Note the error IIN bits set (IIN2.1 is preferred)")
       def run(driver: TestDriver): List[DeferredCheck] = {