diff --git a/tests/foo/1.0/IFooCallback.hal b/tests/foo/1.0/IFooCallback.hal
index 7b25df3..c9fcf77 100644
--- a/tests/foo/1.0/IFooCallback.hal
+++ b/tests/foo/1.0/IFooCallback.hal
@@ -7,4 +7,31 @@
     heyItsYou(IFooCallback cb);
     heyItsYouIsntIt(IFooCallback cb) generates (bool yesOrNo);
     oneway heyItsTheMeaningOfLife(uint8_t tmol);
+
+    // The next two methods are for instrumentation purposes.
+
+    // Block the caller for up to ns nanosesonds and return the number
+    // of nanoseconds it took to invoke each of the three methods
+    // above, both from the point of view of the caller (callerBlockedNs) and
+    // from the point of view of IFooCallback itself (timeNs).  timeNs measures
+    // how long a method's body took to execute, regardless of whether the
+    // method was oneway or two-way.  callerBlockedNs reflects the amount of
+    // time the caller was blocked before the method returned.  For two-way
+    // methods, callerBlockedNs should be slightly higher than timeNs.  For
+    // one-way calls, callerBlockedNs will be very low, and unrelated to
+    // timeNs.
+
+    struct InvokeInfo {
+        bool invoked;
+	int64_t callerBlockedNs;
+	int64_t timeNs;
+    };
+    reportResults(int64_t ns) generates (int64_t leftNs, InvokeInfo[3] invokeInfo);
+
+    // This method is used by the caller of IFooCallback to tell IFooCallback
+    // how long the three methods above took, from the point of view of that
+    // caller.  IFooCallback adds this information to the one reported by
+    // reportResults in InvokeInfo.
+
+    youBlockedMeFor(int64_t[3] callerBlockedInfo);
 };