diff --git a/luprex/core/cpp/sched.cpp b/luprex/core/cpp/sched.cpp
index a10fc405..e061ec50 100644
--- a/luprex/core/cpp/sched.cpp
+++ b/luprex/core/cpp/sched.cpp
@@ -1,5 +1,9 @@
 
 #include "sched.hpp"
+#include "streambuffer.hpp"
+#include "luastack.hpp"
+#include <sstream>
+#include <ostream>
 
 bool SchedEntry::operator < (const SchedEntry &other) const {
     if (clock_ < other.clock_) return true;
@@ -11,6 +15,12 @@ bool SchedEntry::operator < (const SchedEntry &other) const {
     return false;
 }
 
+std::string SchedEntry::debug_string() const {
+    std::ostringstream oss;
+    oss << "(" << clock_ << "," << thread_id_ << "," << place_id_ << ")";
+    return oss.str();
+}
+
 void Schedule::add(int64_t clk, int64_t thid, int64_t plid) {
     schedule_.insert(SchedEntry(clk, thid, plid));
 }
@@ -20,11 +30,20 @@ bool Schedule::ready(int64_t clk) const {
 }
 
 SchedEntry Schedule::pop() {
+    assert(!schedule_.empty());
     SchedEntry result = *schedule_.begin();
     schedule_.erase(schedule_.begin());
     return result;
 }
 
+std::string Schedule::debug_string() {
+    std::ostringstream oss;
+    for (const SchedEntry &se : schedule_) {
+        oss << se.debug_string();
+    }
+    return oss.str();
+}
+
 void Schedule::serialize(StreamBuffer *sb) {
     sb->write_uint32(schedule_.size());
     for (const SchedEntry &entry : schedule_) {
@@ -44,3 +63,41 @@ void Schedule::deserialize(StreamBuffer *sb) {
         add(clock, thread_id, place_id);
     }
 }
+
+LuaDefine(unittests_scheduler, "c") {
+    Schedule s, xs;
+    StreamBuffer sb;
+
+    // Put some stuff into a scheduler.
+    s.add(1, 5, 3);
+    s.add(4, 3, 2);
+    s.add(1, 3, 2);
+    s.add(4, 2, 3);
+
+    // Test serialize and deserialize.
+    LuaAssert(L, s.debug_string() == "(1,3,2)(1,5,3)(4,2,3)(4,3,2)");
+    s.serialize(&sb);
+    xs.deserialize(&sb);
+    LuaAssert(L, xs.debug_string() == "(1,3,2)(1,5,3)(4,2,3)(4,3,2)");
+
+    // Verify that pop, ready, and empty do the right thing.
+    LuaAssert(L, s.ready(0) == false)
+    LuaAssert(L, s.ready(1) == true)
+    LuaAssert(L, s.pop().debug_string() == "(1,3,2)");
+    LuaAssert(L, s.ready(0) == false)
+    LuaAssert(L, s.ready(1) == true)
+    LuaAssert(L, s.pop().debug_string() == "(1,5,3)");
+    LuaAssert(L, s.debug_string() == "(4,2,3)(4,3,2)");
+    LuaAssert(L, s.pop().debug_string() == "(4,2,3)");
+    LuaAssert(L, s.pop().debug_string() == "(4,3,2)");
+    LuaAssert(L, s.ready(10000) == false);
+    LuaAssert(L, s.empty());
+    LuaAssert(L, s.debug_string() == "");
+
+    // Test serialization of an empty streambuffer.
+    s.serialize(&sb);
+    xs.deserialize(&sb);
+    LuaAssert(L, xs.debug_string() == "");
+
+    return 0;
+}
diff --git a/luprex/core/cpp/sched.hpp b/luprex/core/cpp/sched.hpp
index 8412b7b4..252cc6a0 100644
--- a/luprex/core/cpp/sched.hpp
+++ b/luprex/core/cpp/sched.hpp
@@ -24,6 +24,8 @@ public:
     }
 
     bool operator < (const SchedEntry &other) const;
+
+    std::string debug_string() const;
 };
 
 class Schedule {
@@ -32,7 +34,9 @@ private:
 public:
     void add(int64_t clk, int64_t thid, int64_t plid);
     bool ready(int64_t clk) const;
+    bool empty() const { return schedule_.empty(); }
     SchedEntry pop();
+    std::string debug_string();
 
     void serialize(StreamBuffer *sb);
     void deserialize(StreamBuffer *sb);