diff --git a/modules/core/shared/src/test/scala/InMemory.scala b/modules/core/shared/src/test/scala/InMemory.scala
index eecc8a13..a2f600a1 100644
--- a/modules/core/shared/src/test/scala/InMemory.scala
+++ b/modules/core/shared/src/test/scala/InMemory.scala
@@ -7,7 +7,7 @@ package natchez
 import java.net.URI
 
 import cats.data.{Chain, Kleisli}
-import cats.effect.{IO, Ref, Resource}
+import cats.effect.{IO, MonadCancelThrow, Ref, Resource}
 
 import natchez.Span.Options
 import munit.CatsEffectSuite
@@ -118,15 +118,15 @@ trait InMemorySuite extends CatsEffectSuite {
   val NatchezCommand = InMemory.NatchezCommand
 
   trait TraceTest {
-    def program[F[_]: Trace]: F[Unit]
+    def program[F[_]: MonadCancelThrow: Trace]: F[Unit]
     def expectedHistory: List[(Lineage, NatchezCommand)]
   }
 
   def traceTest(name: String, tt: TraceTest) = {
     test(s"$name - Kleisli")(
-      testTraceKleisli(tt.program[Kleisli[IO, Span[IO], *]](_), tt.expectedHistory)
+      testTraceKleisli(tt.program[Kleisli[IO, Span[IO], *]](implicitly, _), tt.expectedHistory)
     )
-    test(s"$name - IOLocal")(testTraceIoLocal(tt.program[IO](_), tt.expectedHistory))
+    test(s"$name - IOLocal")(testTraceIoLocal(tt.program[IO](implicitly, _), tt.expectedHistory))
   }
 
   def testTraceKleisli(
diff --git a/modules/core/shared/src/test/scala/SpanCoalesceTest.scala b/modules/core/shared/src/test/scala/SpanCoalesceTest.scala
index a4c693e9..ac44a0f0 100644
--- a/modules/core/shared/src/test/scala/SpanCoalesceTest.scala
+++ b/modules/core/shared/src/test/scala/SpanCoalesceTest.scala
@@ -4,12 +4,14 @@
 
 package natchez
 
+import cats.effect.MonadCancelThrow
+
 class SpanCoalesceTest extends InMemorySuite {
 
   traceTest(
     "suppress - nominal",
     new TraceTest {
-      def program[F[_]: Trace] = {
+      def program[F[_]: MonadCancelThrow: Trace] = {
         def detailed =
           Trace[F].span("parent")(Trace[F].span("child")(Trace[F].put("answer" -> 42)))
         Trace[F].span("suppressed", Span.Options.Suppress)(detailed)
@@ -27,7 +29,7 @@ class SpanCoalesceTest extends InMemorySuite {
   traceTest(
     "coaslesce - nominal",
     new TraceTest {
-      def program[F[_]: Trace] = {
+      def program[F[_]: MonadCancelThrow: Trace] = {
         def detailed =
           Trace[F].span("parent")(Trace[F].span("child")(Trace[F].put("answer" -> 42)))
         Trace[F].span("coalesced", Span.Options.Coalesce)(detailed)
diff --git a/modules/core/shared/src/test/scala/SpanPropagationTest.scala b/modules/core/shared/src/test/scala/SpanPropagationTest.scala
index 13893e74..9d698121 100644
--- a/modules/core/shared/src/test/scala/SpanPropagationTest.scala
+++ b/modules/core/shared/src/test/scala/SpanPropagationTest.scala
@@ -4,12 +4,15 @@
 
 package natchez
 
+import cats.effect.MonadCancelThrow
+import cats.syntax.all._
+
 class SpanPropagationTest extends InMemorySuite {
 
   traceTest(
     "propagation",
     new TraceTest {
-      def program[F[_]: Trace] =
+      def program[F[_]: MonadCancelThrow: Trace] =
         Trace[F].span("parent")(Trace[F].span("child")(Trace[F].put("answer" -> 42)))
 
       def expectedHistory = List(
@@ -23,4 +26,27 @@ class SpanPropagationTest extends InMemorySuite {
       )
     }
   )
+
+  traceTest(
+    "spanR",
+    new TraceTest {
+      def program[F[_]: MonadCancelThrow: Trace] =
+        Trace[F].spanR("spanR").use { f =>
+          Trace[F].span("span")(
+            f(Trace[F].put("question" -> "ultimate")) *> Trace[F].put("answer" -> 42)
+          )
+        }
+
+      def expectedHistory = List(
+        (Lineage.Root, NatchezCommand.CreateRootSpan("root", Kernel(Map()))),
+        (Lineage.Root, NatchezCommand.CreateSpan("spanR", None)),
+        (Lineage.Root, NatchezCommand.CreateSpan("span", None)),
+        (Lineage.Root / "spanR", NatchezCommand.Put(List("question" -> "ultimate"))),
+        (Lineage.Root / "span", NatchezCommand.Put(List("answer" -> 42))),
+        (Lineage.Root, NatchezCommand.ReleaseSpan("span")),
+        (Lineage.Root, NatchezCommand.ReleaseSpan("spanR")),
+        (Lineage.Root, NatchezCommand.ReleaseRootSpan("root"))
+      )
+    }
+  )
 }