diff --git a/groundtest/src/main/scala/cachetest.scala b/groundtest/src/main/scala/cachetest.scala
index 07dbe9ce..ac6a5c54 100644
--- a/groundtest/src/main/scala/cachetest.scala
+++ b/groundtest/src/main/scala/cachetest.scala
@@ -43,5 +43,7 @@ class CacheFillTest(implicit p: Parameters) extends GroundTest()(p)
   when (state === s_prefetch && round_done) { state := s_retrieve }
   when (state === s_retrieve && round_done) { state := s_finished }
 
-  io.finished := (state === s_finished)
+  io.status.finished := (state === s_finished)
+  io.status.timeout.valid := Bool(false)
+  io.status.error.valid := Bool(false)
 }
diff --git a/groundtest/src/main/scala/comparator.scala b/groundtest/src/main/scala/comparator.scala
index f32dcbde..f7451236 100644
--- a/groundtest/src/main/scala/comparator.scala
+++ b/groundtest/src/main/scala/comparator.scala
@@ -208,6 +208,7 @@ class ComparatorClient(val target: Long)(implicit val p: Parameters) extends Mod
     val tl  = new ClientUncachedTileLinkIO()
     val out = Decoupled(new Grant)
     val finished = Bool(OUTPUT)
+    val timeout = Bool(OUTPUT)
   }
 
   val xacts = tlMaxClientXacts
@@ -295,15 +296,18 @@ class ComparatorClient(val target: Long)(implicit val p: Parameters) extends Mod
   timer.io.stop.valid  := io.tl.grant.fire() && io.tl.grant.bits.first()
   timer.io.stop.bits   := io.tl.grant.bits.client_xact_id
   assert(!timer.io.timeout, "Comparator TL client timed out")
+  io.timeout := timer.io.timeout
 }
 
 class ComparatorSink(implicit val p: Parameters) extends Module
     with HasComparatorParameters
     with HasTileLinkParameters
+    with HasGroundTestConstants
 {
   val io = new Bundle {
     val in = Vec(nTargets, Decoupled(new Grant)).flip
     val finished = Bool(OUTPUT)
+    val error = Valid(UInt(width = errorCodeBits))
   }
   
   // could use a smaller Queue here, but would couple targets flow controls together
@@ -321,10 +325,23 @@ class ComparatorSink(implicit val p: Parameters) extends Module
       printf("%d: %x =/= %x, g_type = %x\n", idx, base.data, g.data, g.g_type)
     }
 
+    val assert_conds = Seq(
+      g.is_builtin_type,
+      base.g_type === g.g_type,
+      base.addr_beat === g.addr_beat || !g.hasData(),
+      base.data === g.data || !g.hasData())
+
     assert (g.is_builtin_type, "grant not builtin")
     assert (base.g_type === g.g_type, "g_type mismatch")
     assert (base.addr_beat === g.addr_beat || !g.hasData(), "addr_beat mismatch")
     assert (base.data === g.data || !g.hasData(), "data mismatch")
+
+    assert_conds.zipWithIndex.foreach { case (cond, i) =>
+      when (cond) {
+        io.error.valid := Bool(true)
+        io.error.bits := UInt(i)
+      }
+    }
   }
   when (all_valid) {
     // Skip the results generated by the block wiping
@@ -355,6 +372,13 @@ class ComparatorCore(implicit p: Parameters) extends GroundTest()(p)
     sink.io.in(index) <> client.io.out
     client
   }
+  val client_timeouts = clients.map(_.io.timeout)
   
-  io.finished := source.io.finished && sink.io.finished && clients.map(_.io.finished).reduce(_ && _)
+  io.status.finished := source.io.finished && sink.io.finished && clients.map(_.io.finished).reduce(_ && _)
+  io.status.timeout.valid := client_timeouts.reduce(_ || _)
+  io.status.timeout.bits := MuxCase(UInt(0),
+    client_timeouts.zipWithIndex.map {
+      case (timeout, i) => (timeout -> UInt(i))
+    })
+  io.status.error := sink.io.error
 }
diff --git a/groundtest/src/main/scala/dmatest.scala b/groundtest/src/main/scala/dmatest.scala
deleted file mode 100644
index d2c1cbb9..00000000
--- a/groundtest/src/main/scala/dmatest.scala
+++ /dev/null
@@ -1,231 +0,0 @@
-package groundtest
-
-import Chisel._
-import uncore.tilelink._
-import uncore.devices._
-import uncore.devices.DmaRequest._
-import uncore.util._
-import uncore.constants._
-import rocket._
-import junctions.{PAddrBits, HasAddrMapParameters}
-import cde.{Parameters, Field}
-import scala.math.max
-
-case class DmaTestCase(source: Int, dest: Int, length: Int)
-
-object DmaTestCases {
-  def apply(cases: (Int, Int, Int) *): Seq[DmaTestCase] = {
-    cases.toSeq.map {
-      case (source, dest, length) => DmaTestCase(source, dest, length)
-    }
-  }
-}
-
-case class DmaStreamTestConfig(
-  source: Int, dest: Int, len: Int, size: Int)
-
-case object DmaTestSet extends Field[Seq[DmaTestCase]]
-case object DmaTestDataStart extends Field[Int]
-case object DmaTestDataStride extends Field[Int]
-
-case object DmaStreamTestSettings extends Field[DmaStreamTestConfig]
-
-class DmaStatusReg(implicit val p: Parameters) extends Module
-    with HasDmaParameters with HasTileLinkParameters {
-
-  val io = new Bundle {
-    val csr = (new RoCCCSRs).flip
-    val incr_outstanding = Bool(INPUT)
-    val xact_outstanding = Bool(OUTPUT)
-    val resp_status = UInt(OUTPUT, dmaStatusBits)
-  }
-
-  val status_reg = Reg(UInt(width = dmaStatusBits))
-
-  val outstanding_cnt = TwoWayCounter(
-    io.incr_outstanding, io.csr.wen, tlMaxClientXacts)
-
-  when (io.csr.wen) { status_reg := io.csr.wdata }
-
-  io.xact_outstanding := outstanding_cnt > UInt(0)
-  io.resp_status := status_reg
-  io.csr.rdata(0) := status_reg
-}
-
-class DmaStreamTest(implicit p: Parameters) extends GroundTest()(p)
-    with HasDmaParameters with HasCoreParameters with HasAddrMapParameters {
-  val (s_start :: s_setup_req :: s_setup_wait ::
-       s_stream_out :: s_stream_in ::  s_stream_wait ::
-       s_check_req :: s_check_wait :: s_done :: Nil) = Enum(Bits(), 9)
-  val state = Reg(init = s_start)
-  val lo_base = addrMap("devices:loopback").start
-  val conf = p(DmaStreamTestSettings)
-
-  val test_data = Vec.tabulate(conf.len) { i => UInt(i * 8, conf.size * 8) }
-
-  val (req_index, req_done) = Counter(io.cache.head.req.fire(), conf.len)
-  val (resp_index, resp_done) = Counter(io.cache.head.resp.fire(), conf.len)
-
-  val out_req = ClientDmaRequest(
-    cmd = DMA_CMD_SOUT,
-    src_start = UInt(conf.source),
-    dst_start = UInt(lo_base),
-    segment_size = UInt(conf.len * conf.size),
-    word_size = UInt(log2Up(conf.size)))
-
-  val in_req = ClientDmaRequest(
-    cmd = DMA_CMD_SIN,
-    src_start = UInt(lo_base),
-    dst_start = UInt(conf.dest),
-    segment_size = UInt(conf.len * conf.size),
-    word_size = UInt(log2Up(conf.size)))
-
-  val frontend = Module(new DmaFrontend)
-  frontend.io.cpu.req.valid := (state === s_stream_out) || (state === s_stream_in)
-  frontend.io.cpu.req.bits := Mux(state === s_stream_out, out_req, in_req)
-
-  io.ptw.head <> frontend.io.ptw
-  io.mem.head <> frontend.io.mem
-
-  val status_reg = Module(new DmaStatusReg)
-  //status_reg.io.csr <> io.csr
-  status_reg.io.incr_outstanding := frontend.io.incr_outstanding
-
-  val cache_addr_base = Mux(state === s_setup_req, UInt(conf.source), UInt(conf.dest))
-  val cache_req = io.cache.head.req
-
-  cache_req.valid := (state === s_setup_req) || (state === s_check_req)
-  cache_req.bits.addr := cache_addr_base + Cat(req_index, UInt(0, log2Up(conf.size)))
-  cache_req.bits.data := test_data(req_index)
-  cache_req.bits.typ  := UInt(log2Up(conf.size))
-  cache_req.bits.cmd  := Mux(state === s_setup_req, M_XWR, M_XRD)
-
-  when (state === s_start) { state := s_setup_req }
-  when (state === s_setup_req && req_done) { state := s_setup_wait }
-  when (state === s_check_req && req_done) { state := s_check_wait }
-  when (state === s_setup_wait && resp_done) { state := s_stream_out }
-  when (state === s_check_wait && resp_done) { state := s_done }
-
-  when (frontend.io.cpu.req.fire()) {
-    state := Mux(state === s_stream_out, s_stream_in, s_stream_wait)
-  }
-
-  val dma_done = (state === s_stream_wait) &&
-    !frontend.io.busy && !status_reg.io.xact_outstanding
-
-  when (dma_done) { state := s_check_req }
-
-  val resp_data = io.cache.head.resp.bits.data(conf.size * 8 - 1, 0)
-  assert(!io.cache.head.resp.valid || !io.cache.head.resp.bits.has_data ||
-         resp_data === test_data(resp_index),
-         "Result data streamed in does not match data streamed out")
-  assert(!frontend.io.cpu.resp.valid || frontend.io.cpu.resp.bits.status === UInt(0),
-          "Frontend error response")
-
-  io.finished := (state === s_done)
-}
-
-class DmaTest(implicit p: Parameters) extends GroundTest()(p)
-    with HasDmaParameters with HasCoreParameters {
-
-  private val testSet = p(DmaTestSet)
-  private val dataStart = p(DmaTestDataStart)
-  private val dataStride = p(DmaTestDataStride)
-  private val wordBits = 32
-  private val wordBytes = wordBits / 8
-  private val pAddrBits = p(PAddrBits)
-
-  val sourceAddrs = Vec(testSet.map(test => UInt(test.source)))
-  val destAddrs = Vec(testSet.map(test => UInt(test.dest)))
-  val transferLengths = Vec(testSet.map(test => UInt(test.length)))
-  val testIdx = Reg(init = UInt(0, log2Up(testSet.size)))
-
-  val (s_start :: s_fill_req :: s_fill_resp :: s_copy_req :: s_copy_wait ::
-       s_check_req :: s_check_resp :: s_finished :: Nil) = Enum(Bits(), 8)
-  val state = Reg(init = s_start)
-
-  val req_data = Reg(UInt(width = wordBits))
-  val req_addr = Reg(UInt(width = pAddrBits))
-  val bytes_left = Reg(UInt(width = pAddrBits))
-  val prefetch = sourceAddrs(testIdx) === destAddrs(testIdx)
-
-  val frontend = Module(new DmaFrontend)
-  frontend.io.cpu.req.valid := (state === s_copy_req)
-  frontend.io.cpu.req.bits := ClientDmaRequest(
-    cmd = Mux(prefetch, DMA_CMD_PFR, DMA_CMD_COPY),
-    src_start = sourceAddrs(testIdx),
-    dst_start = destAddrs(testIdx),
-    segment_size = transferLengths(testIdx))
-
-  io.ptw.head <> frontend.io.ptw
-  io.mem.head <> frontend.io.mem
-
-  val status_reg = Module(new DmaStatusReg)
-  //status_reg.io.csr <> io.csr
-  status_reg.io.incr_outstanding := frontend.io.incr_outstanding
-
-  val dma_done = !frontend.io.busy && !status_reg.io.xact_outstanding
-
-  val cache_resp = io.cache.head.resp
-  val cache_req = io.cache.head.req
-  cache_req.valid := (state === s_fill_req) || (state === s_check_req)
-  cache_req.bits.addr := req_addr
-  cache_req.bits.data := req_data
-  cache_req.bits.typ  := MT_W
-  cache_req.bits.cmd  := Mux(state === s_fill_req, M_XWR, M_XRD)
-
-  when (state === s_start) {
-    req_addr := sourceAddrs(testIdx)
-    req_data := UInt(dataStart)
-    bytes_left := transferLengths(testIdx)
-    state := s_fill_req
-  }
-
-  when (cache_req.fire()) {
-    req_addr := req_addr + UInt(wordBytes)
-    bytes_left := bytes_left - UInt(wordBytes)
-    state := Mux(state === s_fill_req, s_fill_resp, s_check_resp)
-  }
-
-  when (state === s_fill_resp && cache_resp.valid) {
-    req_data := req_data + UInt(dataStride)
-    state := Mux(bytes_left === UInt(0), s_copy_req, s_fill_req)
-  }
-
-  when (frontend.io.cpu.req.fire()) { state := s_copy_wait }
-
-  when (state === s_copy_wait && dma_done) {
-    req_addr := destAddrs(testIdx)
-    req_data := UInt(dataStart)
-    bytes_left := transferLengths(testIdx)
-    state := s_check_req
-  }
-
-  when (state === s_check_resp && cache_resp.valid) {
-    req_data := req_data + UInt(dataStride)
-    when (bytes_left > UInt(0)) {
-      state := s_check_req
-    } .elsewhen (testIdx === UInt(testSet.size - 1)) {
-      state := s_finished
-    } .otherwise {
-      testIdx := testIdx + UInt(1)
-      state := s_start
-    }
-  }
-
-  io.finished := (state === s_finished)
-
-  testSet.foreach { case DmaTestCase(source, dest, length) =>
-    require(source % wordBytes == 0, "source address must be word-aligned")
-    require(dest % wordBytes == 0, "destination address must be word-aligned")
-    require(length % wordBytes == 0, "transfer length must be word-aligned")
-  }
-
-  assert(!cache_resp.valid || !cache_resp.bits.has_data ||
-    cache_resp.bits.data === req_data, "Received data does not match")
-  assert(!frontend.io.cpu.resp.valid || frontend.io.cpu.resp.bits.status === UInt(0),
-          "Frontend error response")
-
-  val cache_timeout = Timer(1000, cache_req.fire(), cache_resp.valid)
-  assert(!cache_timeout, "Memory request timed out")
-}
diff --git a/groundtest/src/main/scala/generator.scala b/groundtest/src/main/scala/generator.scala
index 84aad6a5..9fbb2098 100644
--- a/groundtest/src/main/scala/generator.scala
+++ b/groundtest/src/main/scala/generator.scala
@@ -39,7 +39,7 @@ class UncachedTileLinkGenerator(id: Int)
 
   val io = new Bundle {
     val mem = new ClientUncachedTileLinkIO
-    val finished = Bool(OUTPUT)
+    val status = new GroundTestStatus
   }
 
   val (s_start :: s_put :: s_get :: s_finished :: Nil) = Enum(Bits(), 4)
@@ -61,7 +61,9 @@ class UncachedTileLinkGenerator(id: Int)
   val timeout = Timer(genTimeout, io.mem.acquire.fire(), io.mem.grant.fire())
   assert(!timeout, s"Uncached generator ${id} timed out waiting for grant")
 
-  io.finished := (state === s_finished)
+  io.status.finished := (state === s_finished)
+  io.status.timeout.valid := timeout
+  io.status.timeout.bits := UInt(id)
 
   val part_of_full_addr =
     if (log2Ceil(nGens) > 0) {
@@ -99,17 +101,22 @@ class UncachedTileLinkGenerator(id: Int)
     operand_size = wordSize,
     alloc = Bool(false))
 
-  io.mem.acquire.valid := sending && !io.finished
+  io.mem.acquire.valid := sending && !io.status.finished
   io.mem.acquire.bits := Mux(state === s_put, put_acquire, get_acquire)
-  io.mem.grant.ready := !sending && !io.finished
+  io.mem.grant.ready := !sending && !io.status.finished
 
   def wordFromBeat(addr: UInt, dat: UInt) = {
     val shift = Cat(beatOffset(addr), UInt(0, wordOffset + 3))
     (dat >> shift)(genWordBits - 1, 0)
   }
 
-  assert(!io.mem.grant.valid || state =/= s_get ||
-    wordFromBeat(full_addr, io.mem.grant.bits.data) === word_data,
+  val data_mismatch = io.mem.grant.fire() && state === s_get &&
+    wordFromBeat(full_addr, io.mem.grant.bits.data) =/= word_data
+
+  io.status.error.valid := data_mismatch
+  io.status.error.bits := UInt(id)
+
+  assert(!data_mismatch,
     s"Get received incorrect data in uncached generator ${id}")
 
   def beatOffset(addr: UInt) = // TODO zero-width
@@ -121,11 +128,13 @@ class HellaCacheGenerator(id: Int)
     (implicit p: Parameters) extends L1HellaCacheModule()(p) with HasGeneratorParameters {
   val io = new Bundle {
     val mem = new HellaCacheIO
-    val finished = Bool(OUTPUT)
+    val status = new GroundTestStatus
   }
 
   val timeout = Timer(genTimeout, io.mem.req.fire(), io.mem.resp.valid)
   assert(!timeout, s"Cached generator ${id} timed out waiting for response")
+  io.status.timeout.valid := timeout
+  io.status.timeout.bits := UInt(id)
 
   val (s_start :: s_write :: s_read :: s_finished :: Nil) = Enum(Bits(), 4)
   val state = Reg(init = s_start)
@@ -143,7 +152,7 @@ class HellaCacheGenerator(id: Int)
   val req_addr = UInt(startAddress) + Cat(req_cnt, part_of_req_addr)
   val req_data = Cat(UInt(id, log2Up(nGens)), req_addr)
 
-  io.mem.req.valid := sending && !io.finished
+  io.mem.req.valid := sending && !io.status.finished
   io.mem.req.bits.addr := req_addr
   io.mem.req.bits.data := req_data
   io.mem.req.bits.typ  := wordSize
@@ -157,7 +166,7 @@ class HellaCacheGenerator(id: Int)
 
   when (req_wrap) { state := Mux(state === s_write, s_read, s_finished) }
 
-  io.finished := (state === s_finished)
+  io.status.finished := (state === s_finished)
 
   def data_match(recv: Bits, expected: Bits): Bool = {
     val recv_resized = Wire(Bits(width = genWordBits))
@@ -168,8 +177,13 @@ class HellaCacheGenerator(id: Int)
     recv_resized === exp_resized
   }
 
-  assert(!io.mem.resp.valid || !io.mem.resp.bits.has_data ||
-    data_match(io.mem.resp.bits.data, req_data),
+  val data_mismatch = io.mem.resp.valid && io.mem.resp.bits.has_data &&
+    !data_match(io.mem.resp.bits.data, req_data)
+
+  io.status.error.valid := data_mismatch
+  io.status.error.bits := UInt(id)
+
+  assert(!data_mismatch,
     s"Received incorrect data in cached generator ${id}")
 }
 
@@ -193,6 +207,6 @@ class GeneratorTest(implicit p: Parameters)
   io.cache <> cached.map(_.io.mem)
   io.mem <> uncached.map(_.io.mem)
 
-  val gen_finished = cached.map(_.io.finished) ++ uncached.map(_.io.finished)
-  io.finished := gen_finished.reduce(_ && _)
+  val gen_debug = cached.map(_.io.status) ++ uncached.map(_.io.status)
+  io.status := DebugCombiner(gen_debug)
 }
diff --git a/groundtest/src/main/scala/nastitest.scala b/groundtest/src/main/scala/nastitest.scala
index ef662464..a6011c17 100644
--- a/groundtest/src/main/scala/nastitest.scala
+++ b/groundtest/src/main/scala/nastitest.scala
@@ -13,7 +13,7 @@ class NastiGenerator(id: Int)(implicit val p: Parameters) extends Module
     with HasGeneratorParameters {
 
   val io = new Bundle {
-    val finished = Bool(OUTPUT)
+    val status = new GroundTestStatus
     val mem = new NastiIO
   }
 
@@ -65,7 +65,7 @@ class NastiGenerator(id: Int)(implicit val p: Parameters) extends Module
   io.mem.r.ready := Bool(true)
   io.mem.b.ready := Bool(true)
 
-  io.finished := (state === s_finish)
+  io.status.finished := (state === s_finish)
 
   val (read_resp_idx,  read_resp_done)  = Counter(io.mem.r.fire(), maxRequests)
   val read_resp_addr = UInt(startAddress) + Cat(read_resp_idx, part_of_addr)
@@ -73,8 +73,10 @@ class NastiGenerator(id: Int)(implicit val p: Parameters) extends Module
   val read_shift = Cat(read_offset, UInt(0, 3))
   val read_data = (io.mem.r.bits.data >> read_shift)(genWordBits - 1, 0)
 
-  assert(!io.mem.r.valid || read_data === ref_data(read_resp_idx),
-    "NASTI Test: results do not match")
+  val data_mismatch = io.mem.r.valid && read_data =/= ref_data(read_resp_idx)
+  assert(!data_mismatch, "NASTI Test: results do not match")
+  io.status.error.valid := data_mismatch
+  io.status.error.bits := UInt(1)
 
   when (state === s_start) { state := s_write_addr }
   when (io.mem.aw.fire()) { state := s_write_data  }
@@ -96,6 +98,9 @@ class NastiGenerator(id: Int)(implicit val p: Parameters) extends Module
   w_timer.io.stop.valid := io.mem.b.fire()
   w_timer.io.stop.bits := io.mem.b.bits.id
   assert(!w_timer.io.timeout, "NASTI Write timed out")
+
+  io.status.timeout.valid := r_timer.io.timeout || w_timer.io.timeout
+  io.status.timeout.bits := Mux(r_timer.io.timeout, UInt(1), UInt(2))
 }
 
 class NastiConverterTest(implicit p: Parameters) extends GroundTest()(p)
@@ -112,5 +117,5 @@ class NastiConverterTest(implicit p: Parameters) extends GroundTest()(p)
 
   converter.io.nasti <> test.io.mem
   TileLinkWidthAdapter(io.mem.head, converter.io.tl)
-  io.finished := test.io.finished
+  io.status := test.io.status
 }
diff --git a/groundtest/src/main/scala/regression.scala b/groundtest/src/main/scala/regression.scala
index 3822d293..f7e60594 100644
--- a/groundtest/src/main/scala/regression.scala
+++ b/groundtest/src/main/scala/regression.scala
@@ -13,6 +13,7 @@ class RegressionIO(implicit val p: Parameters) extends ParameterizedBundle()(p)
   val cache = new HellaCacheIO
   val mem = new ClientUncachedTileLinkIO
   val finished = Bool(OUTPUT)
+  val errored = Bool(OUTPUT)
 }
 
 abstract class Regression(implicit val p: Parameters)
@@ -178,10 +179,11 @@ class NoAllocPutHitRegression(implicit p: Parameters) extends Regression()(p) {
     }
   }
 
-  assert(!io.mem.grant.valid || !gnt.hasData() || gnt.data === test_data,
-    "NoAllocPutHitRegression: data does not match")
+  val data_mismatch = io.mem.grant.fire() && gnt.hasData() && gnt.data =/= test_data
+  assert(!data_mismatch, "NoAllocPutHitRegression: data does not match")
 
   io.finished := (state === s_done)
+  io.errored := data_mismatch
 
   disableCache()
 }
@@ -249,9 +251,10 @@ class MixedAllocPutRegression(implicit p: Parameters) extends Regression()(p) {
 
   io.finished := (state === s_done)
 
-  assert(state =/= s_get_wait || !io.mem.grant.valid ||
-         io.mem.grant.bits.data === test_data(io.mem.grant.bits.client_xact_id),
-         "MixedAllocPutRegression: data mismatch")
+  val data_mismatch = state === s_get_wait && io.mem.grant.fire() &&
+    io.mem.grant.bits.data =/= test_data(io.mem.grant.bits.client_xact_id)
+  assert(!data_mismatch, "MixedAllocPutRegression: data mismatch")
+  io.errored := data_mismatch
 
   disableCache()
 }
@@ -347,11 +350,10 @@ class WriteMaskedPutBlockRegression(implicit p: Parameters) extends Regression()
 
   io.finished := (state === s_done)
 
-  assert(!io.mem.grant.valid ||
-         !io.mem.grant.bits.hasData() ||
-         stage === UInt(0) ||
-         io.mem.grant.bits.data === get_data,
-         "WriteMaskedPutBlockRegression: data does not match")
+  val data_mismatch = io.mem.grant.fire() && io.mem.grant.bits.hasData() &&
+                      state =/= UInt(0) && io.mem.grant.bits.data =/= get_data
+  assert(!data_mismatch, "WriteMaskedPutBlockRegression: data does not match")
+  io.errored := data_mismatch
 }
 
 /* Make sure a prefetch that hits returns immediately. */
@@ -379,6 +381,7 @@ class PrefetchHitRegression(implicit p: Parameters) extends Regression()(p) {
   when (sending && pf_done) { sending := Bool(false) }
 
   io.finished := acked.andR
+  io.errored := Bool(false)
 }
 
 /* This tests the sort of access the pattern that Hwacha uses.
@@ -408,8 +411,9 @@ class SequentialSameIdGetRegression(implicit p: Parameters) extends Regression()
 
   io.finished := finished
 
-  assert(!io.mem.grant.valid || io.mem.grant.bits.addr_beat === recv_cnt,
-    "SequentialSameIdGetRegression: grant received out of order")
+  val beat_mismatch = io.mem.grant.fire() && io.mem.grant.bits.addr_beat =/= recv_cnt
+  assert(!beat_mismatch, "SequentialSameIdGetRegression: grant received out of order")
+  io.errored := beat_mismatch
 }
 
 /* Test that a writeback will occur by writing nWays + 1 blocks to the same
@@ -463,9 +467,10 @@ class WritebackRegression(implicit p: Parameters) extends Regression()(p) {
 
   io.finished := (state === s_done)
 
-  assert(!io.mem.grant.valid || !io.mem.grant.bits.hasData() ||
-    io.mem.grant.bits.data === data(ack_cnt),
-    "WritebackRegression: incorrect data")
+  val data_mismatch = io.mem.grant.fire() && io.mem.grant.bits.hasData() &&
+                      io.mem.grant.bits.data =/= data(ack_cnt)
+  assert(!data_mismatch, "WritebackRegression: incorrect data")
+  io.errored := data_mismatch
 }
 
 class ReleaseRegression(implicit p: Parameters) extends Regression()(p) {
@@ -506,9 +511,10 @@ class ReleaseRegression(implicit p: Parameters) extends Regression()(p) {
 
   io.finished := (state === s_done)
 
-  assert(!io.cache.resp.valid || !io.cache.resp.bits.has_data ||
-         io.cache.resp.bits.data === data(resp_idx),
-         "ReleaseRegression: data mismatch")
+  val data_mismatch = io.cache.resp.valid && io.cache.resp.bits.has_data &&
+                      io.cache.resp.bits.data =/= data(resp_idx)
+  assert(!data_mismatch, "ReleaseRegression: data mismatch")
+  io.errored := data_mismatch
 }
 
 class PutBeforePutBlockRegression(implicit p: Parameters) extends Regression()(p) {
@@ -548,6 +554,7 @@ class PutBeforePutBlockRegression(implicit p: Parameters) extends Regression()(p
   when (all_acked) { state := s_finished }
 
   io.finished := (state === s_finished)
+  io.errored := Bool(false)
 }
 
 object RegressionTests {
@@ -610,6 +617,8 @@ class RegressionTest(implicit p: Parameters) extends GroundTest()(p) {
       io.cache.head.req.valid := regress.io.cache.req.valid
       io.cache.head.req.bits := regress.io.cache.req.bits
       io.cache.head.invalidate_lr := regress.io.cache.invalidate_lr
+      io.status.error.valid := regress.io.errored
+      io.status.error.bits := UInt(i)
       cur_finished := regress.io.finished
     }
   }
@@ -620,11 +629,18 @@ class RegressionTest(implicit p: Parameters) extends GroundTest()(p) {
   }
   when (start) { start := Bool(false) }
 
-  io.finished := all_done
-
   val timeout = Timer(5000, start, cur_finished)
   assert(!timeout, "Regression timed out")
 
+  io.status.finished := all_done
+  io.status.timeout.valid := timeout
+  io.status.timeout.bits := UInt(0)
+
   assert(!(all_done && io.mem.head.grant.valid),
     "Getting grant after test completion")
+
+  when (all_done) {
+    io.status.error.valid := io.mem.head.grant.valid
+    io.status.error.bits := UInt(regressions.size)
+  }
 }
diff --git a/groundtest/src/main/scala/tile.scala b/groundtest/src/main/scala/tile.scala
index e2203f7a..9d2c5859 100644
--- a/groundtest/src/main/scala/tile.scala
+++ b/groundtest/src/main/scala/tile.scala
@@ -16,6 +16,11 @@ case class GroundTestTileSettings(
 case object GroundTestKey extends Field[Seq[GroundTestTileSettings]]
 case object GroundTestId extends Field[Int]
 
+trait HasGroundTestConstants {
+  val timeoutCodeBits = 4
+  val errorCodeBits = 4
+}
+
 trait HasGroundTestParameters extends HasAddrMapParameters {
   implicit val p: Parameters
   val tileId = p(GroundTestId)
@@ -69,12 +74,18 @@ class DummyPTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
   }
 }
 
+class GroundTestStatus extends Bundle with HasGroundTestConstants {
+  val finished = Bool(OUTPUT)
+  val timeout = Valid(UInt(width = timeoutCodeBits))
+  val error = Valid(UInt(width = errorCodeBits))
+}
+
 class GroundTestIO(implicit val p: Parameters) extends ParameterizedBundle()(p)
     with HasGroundTestParameters {
   val cache = Vec(nCached, new HellaCacheIO)
   val mem = Vec(nUncached, new ClientUncachedTileLinkIO)
   val ptw = Vec(nPTW, new TLBPTWIO)
-  val finished = Bool(OUTPUT)
+  val status = new GroundTestStatus
 }
 
 abstract class GroundTest(implicit val p: Parameters) extends Module
@@ -113,7 +124,7 @@ class GroundTestTile(resetSignal: Bool)
     ptwPorts += dcache_io.ptw
   }
 
-  when (test.io.finished) { stop() }
+  when (test.io.status.finished) { stop() }
 
   if (ptwPorts.size > 0) {
     val ptw = Module(new DummyPTW(ptwPorts.size))
diff --git a/groundtest/src/main/scala/tracegen.scala b/groundtest/src/main/scala/tracegen.scala
index ca42f580..dd9ce022 100644
--- a/groundtest/src/main/scala/tracegen.scala
+++ b/groundtest/src/main/scala/tracegen.scala
@@ -178,6 +178,7 @@ class TraceGenerator(id: Int)
                                 with HasTraceGenParams {
   val io = new Bundle {
     val finished = Bool(OUTPUT)
+    val timeout = Bool(OUTPUT)
     val mem = new HellaCacheIO
   }
 
@@ -540,6 +541,7 @@ class TraceGenerator(id: Int)
   }
 
   io.finished := Bool(false)
+  io.timeout := timeout
 }
 
 // =======================
@@ -552,5 +554,8 @@ class GroundTestTraceGenerator(implicit p: Parameters)
   val traceGen = Module(new TraceGenerator(p(GroundTestId)))
   io.cache.head <> traceGen.io.mem
 
-  io.finished := traceGen.io.finished
+  io.status.finished := traceGen.io.finished
+  io.status.timeout.valid := traceGen.io.timeout
+  io.status.timeout.bits := UInt(0)
+  io.status.error.valid := Bool(false)
 }
diff --git a/groundtest/src/main/scala/unittest.scala b/groundtest/src/main/scala/unittest.scala
index 4950d212..5144dbb0 100644
--- a/groundtest/src/main/scala/unittest.scala
+++ b/groundtest/src/main/scala/unittest.scala
@@ -576,10 +576,16 @@ class UnitTestSuite(implicit p: Parameters) extends GroundTest()(p) {
   when (state === s_idle) { state := s_start }
   when (state === s_start) { state := s_wait }
 
+  io.status.timeout.valid := Bool(false)
   tests.zipWithIndex.foreach { case (mod, i) =>
     mod.io.start := (state === s_start)
     val timeout = Timer(1000, mod.io.start, mod.io.finished)
     assert(!timeout, s"UnitTest $i timed out")
+    when (timeout) {
+      io.status.timeout.valid := Bool(true)
+      io.status.timeout.bits := UInt(i)
+    }
   }
-  io.finished := tests.map(_.io.finished).reduce(_ && _)
+  io.status.finished := tests.map(_.io.finished).reduce(_ && _)
+  io.status.error.valid := Bool(false)
 }
diff --git a/groundtest/src/main/scala/util.scala b/groundtest/src/main/scala/util.scala
index ca6fb411..864805f8 100644
--- a/groundtest/src/main/scala/util.scala
+++ b/groundtest/src/main/scala/util.scala
@@ -154,3 +154,26 @@ object Frequency {
     return result
   }
 }
+
+object ValidMux {
+  def apply[T <: Data](v1: ValidIO[T], v2: ValidIO[T]*): ValidIO[T] = {
+    apply(v1 +: v2.toSeq)
+  }
+  def apply[T <: Data](valids: Seq[ValidIO[T]]): ValidIO[T] = {
+    val out = Wire(Valid(valids.head.bits))
+    out.valid := valids.map(_.valid).reduce(_ || _)
+    out.bits := MuxCase(valids.head.bits,
+      valids.map(v => (v.valid -> v.bits)))
+    out
+  }
+}
+
+object DebugCombiner {
+  def apply(debugs: Seq[GroundTestStatus]): GroundTestStatus = {
+    val out = Wire(new GroundTestStatus)
+    out.finished := debugs.map(_.finished).reduce(_ || _)
+    out.timeout  := ValidMux(debugs.map(_.timeout))
+    out.error    := ValidMux(debugs.map(_.error))
+    out
+  }
+}